Stable room temperature magnetic ordering and excellent catalytic activity of mechanically activated high surface area nanosized Ni0.45Zn0.55Fe2O4

Article abstract of DOI:10.1039/c5ra14773e

Herein we report the structural, microstructural, dc magnetic and hyperfine properties along with catalytic activity of mechanosynthesized nanosized Ni_0.45Zn_0.55Fe₂O₄ (～12 nm). The Rietveld refinement of the pow

Full text of DOI:10.1039/c5ra14773e

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Stable room temperature magnetic ordering and
excellent catalytic activity of mechanically
activated high surface area nanosized
Ni0.45Zn0.55Fe2O4†
Cite this: RSC Adv., 2015, 5, 78508
S. Dey,a R. Gomes,b R. Mondal,a S. K. Dey,a P. Dasgupta,c A. Poddar,c V. R. Reddy,d
b
a
*
*
A. Bhaumik and S. Kumar
Herein we report the structural, microstructural, dc magnetic and hyperfine properties along with
catalytic activity of mechanosynthesized nanosized Ni0.45Zn0.55Fe2O4 (ꢀ12 nm). The Rietveld refinement
of the powder X-ray diffraction data, high resolution transmission electron microscopy and the
infield Mossbauer study suggest that the sample is nanosized pure single phase cubic spinel of
¨
ꢀ
Fd3m symmetry with good crystallinity and it possesses equilibrium cation distribution
((Fe3+0.45Zn2+0.55)A[Fe3+1.55Ni2+0.45]BO4). The sample exhibits ferrimagnetic ordering with high saturation
magnetization (MSAT ¼ 53, 72 and 76 emu gꢁ1 at 300, 100 and 10 K, respectively), coercivity (HC ¼ 280,
1200 and 2800 Oe at 300, 100 and 10 K, respectively), collective magnetic excitations, spin canting and
memory effect in dc magnetization. The infield Mossbauer study suggests that the interior region of the
¨
particles is perfectly ferrimagnetic in nature, while the spins at the surface region are ferrimagnetically
coupled but noncollinearly aligned. Despite its nanometric size, the sample does not show
superparamagnetic behavior but rather retains stable magnetic order at room temperature due to
enhancement of stress and surface anisotropy energy caused by high energy ball milling. We have
shown that the presence of collective magnetic state along with surface spin disorder are the underlying
reason for having slow dynamics and memory effect in the sample. Further, the BET (Brunauer–
Emmett–Teller) surface area and the pore volume of the sample are 233 m2 gꢁ1 and 0.475 cm3 gꢁ1
,
respectively. The temperature programmed desorption (TPD) of ammonia suggests that the surface of
this porous material is highly acidic (1.516 mmol gꢁ1). Because of its high surface acidity and BET surface
area the material acts as an efficient heterogeneous catalyst in the one pot synthesis of 3,4-
dihydropyrimidine-2(1H)-ones (DHPMs) by Biginelli condensation reaction. This sample can be used in
magnetic data storage devices, coding, storing and retrieving of binary numbers through magnetic field
change and also as a very efficient heterogeneous, magnetically separable and recyclable catalyst.
Received 25th July 2015
Accepted 7th September 2015
DOI: 10.1039/c5ra14773e
www.rsc.org/advances
ferrites exhibit interesting structural properties and rich crystal
chemistry.9 They are also regarded as an exemplary model
Introduction
system for understanding the underlying mechanism of
superparamagnetism, spin glass like behavior, spin canting
effect and ferrimagnetism.9 The interest in the study on
magnetic properties of nanostructured ferrites is fueled by their
applications in high density data storage devices, magnetic
resonance imaging (as contrast agent), magnetically guided
drug delivery, hyperthermia treatment.9–15 However, with
decreasing particle size the magnetic anisotropy energy liable
to clutch the magnetization along certain orientation
becomes comparable to the thermal energy and due to this the
magnetic moment ips randomly with time. When this
happens, particles lose their magnetic order and become
superparamagnetic.9,16 The stability of magnetic order can be
accomplished by the enhancement of the anisotropy energy.9 In
Among all the currently studied magnetic nanomaterials,
nanometric ferrites are the most popular ones not only for
technological reasons but also due to their importance in
understanding the fundamentals of nanomagnetism.1–9 The
unique physical properties of nanometric ferrites have been the
focus of extensive research in recent years. The nanometric
aDepartment of Physics, Jadavpur University, Kolkata-700 032, India. E-mail:
kumars@phys.jdvu.ac.in
bDepartment of Materials Science, Indian Association for the Cultivation of Science,
Kolkata-700 032, India. E-mail: msab@iacs.res.in
cSaha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, India
dUGC-DAE CSR, University Campus, Khandwa Road, Indore-452001, India
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra14773e
78508 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
recent times, the mechanically activated ferrites have come out attention. To the best of our knowledge, there is no report on
as the potential candidates in the perspective of overcoming the the structural, magnetic, hyperne properties and catalytic
direct clash between need for miniaturization and inherent activity of mechanically activated nanosized Ni0.45Zn0.55Fe2O4.
superparamagnetic character of magnetic nanoparticles.3,9
In this background, we have synthesized the nanosized
It is noteworthy that the stress anisotropy induced by ball Ni0.45Zn0.55Fe2O4 by high energy ball milling, rigorously char-
milling acts as an extra source of anisotropy energy and it helps acterized it by using powder X-ray diffraction (PXRD), trans-
in retaining the stable magnetic order of the nanosized Ni–Zn mission electron microscopy (TEM), scanning electron
ferrite at room temperature.9 A lot of investigations have been microscopy (SEM), energy dispersive X-ray spectroscopy (EDS),
¨
performed on nanometric NixZn1ꢁxFe2O4 ferrites because of and Mossbauer spectroscopic techniques and thoroughly
their high saturation magnetization, chemical stability and bio examined the magnetic and hyperne properties of the sample
degradability.3,9,16–21 The Neel temperature (TN) of mechanically in order to reveal the role of microstrain, cation redistribution
´
milled Ni0.5Zn0.5Fe2O4 increases signicantly (TN ꢀ592 K) and stress anisotropy induced by ball milling in determining
compared to its bulk counterpart (TN ꢀ538 K) due to cation the magnetic and hyperne properties of the sample. Moreover,
redistribution.17 The strengthening of intersublattice JAB inter- we have evaluated the catalytic activity of the sample through
action promoted by the migration of Fe3+ ions from (A) to [B] the synthesis of 3,4-dihydropyridin-2-1H-(ones) (DHPMs) by
site leads to the enhancement of magnetization (MSAT ꢀ 51.3 solvent-free one-pot Biginelli condensation reaction.
and 113.4 emu gꢁ1 at 300 and 10 K, respectively), coercivity (HC
In this context, it is pertinent to mention that the function-
ꢀ 500 and 1000 Oe at 300 and 10 K, respectively) and anisotropy alized 3,4-dihydropyrimidine-2(1H)-ones (DHPMs) can be used
energy of the mechanically milled nanosized (ꢀ25 nm) Ni0.35 for a variety of biological and pharmacological activities which
-
Zn0.65Fe2O4.3 The cation redistribution, chemical inhomoge- include antibacterial, antifungal and antihypertensive as well as
neity and large microstrain result in enhancement of magnetic anticarcinogenic applications. They can act as a/a-adrengenic
order, magnetic ordering temperature (TB ꢀ 240 K), saturation antagonists, neuropeptide mitotic kinesine inhibitors and HIV
magnetization (MSAT ꢀ 42 and 64 emu gꢁ1 at 300 and 10 K, gp-120-CD4 inhibitors.30,31 The synthetic route of such DHPMs
respectively) and coercivity (HC ꢀ 1000 Oe at 10 K) along with follows a one-pot multi-component condensation reaction
subsequent reduction of superparamagnetic relaxation in (Biginelli condensation) between an aldehyde, a b-keto ester
mechanically alloyed Ni0.35Zn0.65Fe2O4 (ꢀ27 nm).21 Reduction and urea. The reaction can be catalyzed by various Lewis and
of magnetization and magnetic ordering temperature of nano- Brønsted acids as well as bases. The drawbacks associated with
sized ferrites caused by surface spin canting and super- homogeneous catalysts are catalyst separation, product isola-
paramagnetic relaxation are well established phenomena but tion, low yield and stringent reaction condition. So an easily
despite some attempts the origin of counterintuitive enhance- removable solid acid catalyst giving high yield of products is
ment of magnetization and magnetic ordering temperature in desirable.32,33 Herein we have studied the role of mechanically
mechanically activated nanometric ferrites is yet not been activated nanosized Ni0.45Zn0.55Fe2O4 as a magnetically remov-
understood properly.
able catalyst for the synthesis of DHPMs for the rst time.
Beside the issues related with magnetism, the ferrite nano-
particles have enormous potential for wide variety of catalytic
applications.22–29 Recently, the nanosized ferrites have emerged
as easily recyclable and recoverable catalysts for various organic
reactions by discarding the hazardous process of separation
and recycling of catalyst using conventional methods.22 This has
immense importance in the eld of green chemistry. For
example, the nanometric CuFe2O4 acts as a competent reusable
initiator in the synthesis of b,g-unsaturated ketones from
different allyl halides and acid chlorides,28 the catalyst–oxidant
Experimental section
Materials
We have used powder oxides of a-Fe2O3, NiO and ZnO. All the
oxides are of 99.99% purity and have been procured from Sigma
Aldrich.
Synthesis
combination of NiFe2O4 and H2O2 has been used in the oxida- Bulk Ni0.45Zn0.55Fe2O4 has been prepared by standard ceramic
tion of thiols to disuldes and suldes to sulfoxides,29 ZnFe2O4 method. At rst all the oxides were mixed together in stoichio-
nano powders have been successfully utilized as a catalyst for metric ratio and then manually grounded in an agate mortar for
the one pot three component synthesis of 4H-pyrans in water14 few hours. Aer that, the mixture was pelletized at a pressure of
while the Ni–Co ferrite nanoparticles are efficient candidate for 20 tons cmꢁ2. The pellets were sintered at 900 C for 12 h and
ꢂ
the reduction of nitro aromatic compounds and photo-oxidative cooled down to room temperature at a rate of 3 C minꢁ1. The
ꢂ
degradation of toxic dyes.27
pellets were grounded again and then paꢂssed through the same
It has been reported that the mechanically activated nano- process of sintering at temperature 950 C. Finally, the sample
sized Ni–Zn ferrites are magnetically superior compared to its was annealed at 700 ꢂC for 12 h and slowly cooled down to the
counterparts synthesized by chemical routes.3,9,16,21 As most of room temperature.
the applications rely on the stability of magnetic order of the
The nanosized Ni0.45Zn0.55Fe2O4 was synthesized by grinding
nanoparticles with time and high magnetization at room course powders of extremely pure Ni0.45Zn0.55Fe2O4 prepared by
temperature therefore the mechanically activated nanosized Ni– standard ceramic method at ambient temperature using Fritsch
Zn ferrites of different compositions deserve much more Planetary Mono Mill Pulverisette 6. The speed of the grinder was
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 78508–78518 | 78509

View Article Online
RSC Advances
Paper
set at 330 rpm. Grinding was carried out for 50 hours with ball mixture was cooled to room temperature and 10 ml ethanol was
to mass ratio of 20 : 1 using Tungsten Carbide vials and balls. added to it and the catalyst was removed magnetically. The
mixture was evaporated to dryness and the resultant solid
product was stirred in water and ltered. The product was
Experimental
washed with hexane and recrystallized from hot ethanol to
The PXRD pattern of the sample was recorded by Bruker D8 obtain in pure form. The products were characterized by 1H and
Advanced Diffractometer using Cu Ka (l ¼ 1.54184 A) radiation 13C NMR and compared with reported values. This procedure
˚
by setting the generator at 40 kV and 40 mA. The data was was followed to prepare all the dihydropyrimidinones.
collected at room temperature (21 ꢂC) over the range of 2q ¼ 15–
80ꢂ with step size and counting time of 0.0199ꢂ and 5 s per step,
respectively. The high resolution transmission electron
Result and discussion
(HRTEM) micrographs of the sample were recorded by JEOL
Structural studies
2100 HRTEM. The FESEM (FEI, INSPECT F50) was used for the
It is well known that the cation redistribution is a common
feature of nanosized ferrites.9 So, to determine the crystal
structure of nanosized ferrite unambiguously the information
about the cation migration is required.9 Therefore, we have
morphological and microstructural characterizations. The
presence of constituent elements in the sample was probed by
BRUKER EDS system attached with the FESEM equipment. The
Fourier transform infrared (FTIR) spectrum of the sample was
recorded by Perkin Elmer spectrometer (Spectrum Two) equip-
ped with attenuated total reectance (ATR) attachment in the
¨
recorded the ineld Mossbauer spectrum of the sample at 10 K
in the presence of 5 T external magnetic eld. The ineld
wave number range of 400–4000 cmꢁ1
.
¨
Mossbauer spectrum exhibits two clear subpatterns (Fig. 1(a)).
The non-zero intensity of the 2nd and 5th line in the ineld
The dc magnetization (M) as a function of temperature (T)
and external magnetic eld (H) was measured using super-
conducting quantum interference device magnetometer
21,35
¨
Mossbauer pattern indicates the presence of spin canting,
which is mainly regarded as a surface phenomena.9,21 Moreover,
many uncommon magnetic features of ferrite nanoparticles
have been explained by core–shell model, where it is assumed
that the spins in the interior region (core) of the particle are
perfectly aligned while the spins at the surface (shell) region are
noncollinear in nature.16,21 To account for the effect of diverse
structural and magnetic character of the surface and core of the
sample together we have tted the ineld spectrum with two
pairs of sextets by assuming that the sample is composed of
ferrimagnetically aligned core (interior region) surrounded by
magnetically disordered shell (surface region). Further, to verify
¨
(Quantm Design, SVSM, USA). The Mossbauer spectra of the
sample were recorded in transmission geometry using constant
acceleration drive (CMTE-250) with a 25 mCi 57Co source. The
¨
Mossbauer spectrum of the sample at 10 K in an external
magnetic eld of 5 T applied parallel to the g-ray direction was
recorded using superconducting magnet (JANIS Super-
OptiMag). The natural iron sample is used as standard. The
¨
Mossbauer spectra of the sample were tted by Recoil
program.34 In all the spectra the solid lines indicate the simu-
lated curves and the solid circles represent experimental data
points.
¨
the validity of this assumption, the without eld Mossbauer
spectrum at 10 K has been tted by four Lorentzian sextets
The N2 adsorption/desorption isotherm of the sample was
recorded in a Quantachrome Instrument Autosorb 1C at 77 K.
The sample was degassed at 453 K for 3 h under high vacuum
before the analysis. Non local density functional theory was
employed for the determination of the pore size distribution
from the N2 adsorption/desorption isotherm. The temperature
programmed desorption (TPD) prole of ammonia over nano-
sized Ni0.45Zn0.55Fe2O4 nanomaterial has been analyzed by
using a thermal conductivity detector (TCD) in a Micromeritics
Chemisorb 2720 instrument. For this experiment, the sample
(372 mg) was rst degassed in ow of He (ow rate 30 cm3) for 2
hours at 100 ꢂC. Then the sample was saturated with 10% NH3
in He at room temperature for 30 minutes. The excess NH3 was
removed by ow of He (ow rate 30 cm3) for 45 minutes and
aer that the temperature programmed desorption of ammonia
(carrier gas He) was studied by heating the sample from room
ꢁ1
ꢂ
ꢂ
temperature to 700 C at a temperature ramp of 10 C min
.
The catalytic reactions were carried out in an Anton Paar
microwave reactor Monowave 300. In a typical reaction b-keto
ester (8 mmol), aldehyde (8 mmol), urea (12 mmol) and our
sample as catalyst (30 mg) were mixed thoroughly and irradi-
Fig. 1 Mossbauer spectra of the sample at (a) 10 K with 5 T external
magnetic field and (b) 10 K fitted by the “Lorentzian site analysis” of the
¨
ꢂ
ated in the reactor for 10 minutes at 120 C under solvent-free
condition. Aer completion of the reaction, the reaction Recoil program.
78510 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
Table 2 Crystal data and refinement parameters obtained by MAUDa
maintaining the relative occupancies of the Fe3+ ions among the
(A) and [B] sites same as those obtained from tting of the
ineld pattern. The simulated and the experimentally observed
patterns are presented in Fig. 1 and the values of hyperne
parameters are listed in Table 1. Following the standard prac-
tice, the pair of sextet with high canting angle and low hyperne
eld (HMF) is assigned to the shell region of the particles,
whereas the pair with high HMF and very small canting is
ascribed to the ferrimagnetically ordered core.3,9 In each pair
the sextet with higher hyperne eld (HMF) and lower isomeric
shi (IS) accounts for the (A) site Fe3+ ions, while the other
sextet with lower HMF and higher IS takes care of the [B] site
Fe3+ ions.3,9 The resultant curves obtained by simulation
and GSASb programs
Parameters
Values
Formulaa,b
Ni0.45Zn0.55Fe2O4
238.06
Formula weighta,b
Crystal systema,b
Space groupa,b
Cubic
ꢀ
Fd3m
Crystallite size (nm)a
11.70(0.06)
2.393(0.4)
8.4150(6)
595.885(2)
8
5.307
84.334
0.020
0.014
1.43
0.0118
0.0105
0.1935
1.727
Microstrain (ꢄ10ꢁ4 a
)
ab (A)
˚
3
Vb [A ]
˚
Zb
Dcalb/g cmꢁ3
mCuKab/mmꢁ1
a
¨
matches well with the experimentally observed Mossbauer
Rwp
a
patterns (Fig. 1) and the values of hyperne parameters
Rexp
GOFa
¨
obtained by tting the ineld and without eld Mossbauer
b
Rwp
spectra are in good agreement with each other (Table 1). From
the calculated values of the canting angles (Table 1) it may be
inferred that the spins at the surface region of the particle is
highly disordered, while the core behaves like almost perfect
ferrimagnetically ordered systems. This endorses the fact that
the basic assumption adopted for the tting of ineld
b
Rp
2b
RF
b
c2
our group earlier.9,21,41,42 The Rietveld renement plot obtained
by using MAUD2.33 is presented in Fig. S1.† The renement
converges with negligible difference between the experimental
and simulated data and satisfactory values of reliability
parameters. The relevant structural, microstructural and reli-
ability parameters are listed in Table 2.
¨
Mossbauer spectrum at 10 K is correct and further conrms that
the particles of the sample are composed of ferrimagnetically
ordered core surrounded by a ferrimagnetic shell with disor-
dered spin structure. The results of ineld and without eld
Mossbauer studies together with suggest that only Fe3+ ions are
¨
present in the sample.3 The ratio of Fe3+A/Fe3+ has been
B
To determine the crystal structure, bond length and bond
angle of the sample more precisely we performed the Rietveld
renement of the PXRD data using GSAS program43 with
EXPGUI interface (Fig. 2).44 The occupancies of the iron ions at
the (A) and [B] sites were provided according to the value of the
calculated from the relative area of the sextets.3 The values of
Fe3+A/Fe3+B at core region and at the surface are 0.291 and 0.298,
respectively. These are nearly equal. The average value of Fe3+
/
A
Fe3+ is 0.2945 and it is used during structural renement for
B
providing the initial occupancies of Fe3+ ions at (A) and [B] site.9
The indexing of the PXRD pattern, initial structural and
microstructural characterization together with phase analysis
were carried out by using NTREOR90 of EXPO2009 package,
DICVOL06 and TREOR90 of Fullprof.2k package, FINDSPACE of
EXPO2009 package and Rietveld based soware package
MAUD2.33.36–40 The details of the methodology adopted for
structural, microstructural and phase analysis was reported by
ratio of Fe3+A/Fe3+ (0.2945) as obtained from the ineld
B
¨
Mossbauer study as initial input. The details of the method-
ology followed here is available in our earlier reports.9 The
results suggest that the sample is a single phase spinel ferrite
ꢀ
and it has crystallized in space group Fd3m of f.c.c. lattice with
structural formula (Zn2+0.55Fe3+
)
[Ni2+0.45Fe3+1.55]BO4. It is
0.45 A
noteworthy that the cation distribution in the sample is almost
equal to the ideal equilibrium value of bulk Ni0.45Zn0.55Fe2O4.
Table 1 Values of zero field and infield Mossbauer parameters of the sample at 10 K determined by Lorentzian profile analysis of Recoil program
¨
Width (mm sꢁ1
)
IS (mm sꢁ1
)
23 (mm sꢁ1
)
Beff (T)
Bhf (T)
A23
qb (degree)
Area (%)
a
Temperature/eld
Site
(ꢃ0.03)
0.25
0.30
0.30
0.35
0.25
0.30
0.30
0.35
(ꢃ0.03)
0.45
0.50
0.45
0.50
0.45
0.50
0.45
0.50
(ꢃ0.03)
0.00
0.01
0.00
0.02
0.00
0.01
0.00
0.02
(ꢃ0.4)
57.0
49.5
58.0
50.0
—
—
—
—
(ꢃ0.4)
52.3c
53.0c
53.0c
55.0c
52.0
53.2
53.1
55.4
(ꢃ0.02)
0.250
1.450
0.002
0.010
—
—
—
—
(ꢃ0.2)
6.9
23.1
15.8
54.2
6.9
23.1
15.8
54.2
10 K/5 T
[Fe3+
[Fe3+
[Fe3+
[Fe3+
[Fe3+
[Fe3+
[Fe3+
[Fe3+
]
20.06
46.80
1.80
4.05
—
—
—
—
A s
]
B s
]
A c
]
B c
10 K/0 T
]
A s
]
B s
]
A c
]
B c
a
Observed HMF (BHF) is the vector sum of the internal HMF and the external applied magnetic eld. b The average canting angle estimated from
the ratio of the intensities of lines 2 and 3 from each subspectra, I2/I3 (A23) according to q ¼ arccos[(4 ꢁ I2/I3)/(4 + I2/I3)]1/2. Where I2/I3 ¼ A23
.
c
Estimated according to the relationship of Beff, Bhf and applied eld.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 78508–78518 | 78511

View Article Online
RSC Advances
Paper
Table
3
Fractional coordinates and occupancy of different ions
obtained by GSAS program
Ions
x
y
z
Occupancy (ꢃ0.002)
Zn(A)
Fe(A)
Fe(B)
Ni(B)
O
1/8
1/8
1/2
1/2
1/8
1/8
1/2
1/2
1/8
1/8
1/2
1/2
0.550
0.450
0.775
0.225
1.000
0.2624(12)
0.2624(12)
0.2624(12)
Fig. 2 The Rietveld refinement plot of the sample using GSAS,
showing the difference (blue color line) between the experimental (red
color symbol) and the simulated pattern (black color line).
The Miller indices and the space group obtained by the Rietveld
structure renement method are in good agreement with JCPDS
database (JCPDS no. 08-0234). Fig. 3 depicts the asymmetric
unit, surroundings of metal and oxygen ions, bond angle and
bond length and the values of structural and microstructural
parameters and fractional coordinates along with the occu-
pancy of different ions are listed in Tables 2 and 3.
HRTEM, FESEM and FTIR study
The transmission electron microscopy and selected area elec-
tron diffraction (SAED) technique were employed for compre-
hensive structural and microstructural (particle size, shape and
crystallinity) characterization of the sample. The TEM micro-
graphs at low and high magnication along with SAED pattern
are shown in Fig. 4. The individual size of the particles in the
sample is in the range of 8–20 nm, the particles in the sample
are of assorted size and irregular shape (Fig. 4(a)–(c)). The
particle size distribution histogram is tted with a log-normal
function and the tting suggests that the average particle size
is ꢀ12 nm, which corroborates the crystallite size obtained from
Fig. 4 (a), (b) and (c) HRTEM micrograph and (d) SAED pattern of the
sample.
the PXRD study. The good polycrystalline nature of the sample
is conrmed by the gleaming lattice fringes in the HRTEM
image (Fig. 4(c)) and prominent Debye–Scherrer rings in the
SAED pattern (Fig. 4(d)).16 The crystallographic “d” values
calculated from the radius of the rings corresponding to the
different lattice spacing are in consonance with the values
obtained from the PXRD study.
The energy dispersive X-ray spectrum of the sample has been
shown in Fig. S2.† The well-resolved peaks originating from the
constituent atoms have been found in the energy range from 0 to
8 keV. The peak attributed to Au La appears as the sample was
coated with gold prior to EDS study. In addition, elemental
mapping (Fig. S3†) also indicates the presence of all the constit-
uent elements (Fe, Ni, Zn and O). The FTIR spectrum of the
sample is shown in Fig. S4.† The absorption bands at about 427
and 538 cmꢁ1 are attributed to the stretching vibrations of the
octahedral and tetrahedral site metal–oxygen bonds, respec-
tively.45 Thus the FTIR study supports the results of PXRD study.
N2 adsorption/desorption analysis
The N2 adsorption/desorption isotherm for the sample is shown
in Fig. 5. This isotherm has the characteristic features of both
Fig. 3 Unit cell of the sample showing the tetrahedral (A) and octa-
hedral [B] sites, along with the bond angles and lengths.
78512 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
technique for TEM sample preparation to prevent the inherent
tendency of agglomerate formation.16 In spite of that agglom-
erates are observed in the HRTEM image (Fig. 4) due to very
high magnetization of the sample. The HRTEM images (Fig. 4)
give no evidences in favor of the presence of intragranular pores
in the sample. It may therefore be inferred that the intergran-
ular pores have been formed in between the boundaries of the
particles. The HRTEM study suggests that the particles in the
sample are of irregular shape and assorted size. The variation in
pore size can be attributed to the irregular shape and assorted
size of the particles.
TPD prole of ammonia
The NH3-TPD prole of the porous sample is presented in Fig. 6
which shows two peaks at temperatures 348 and 558 K. The low
temperature peak represents weak acidic site and is compara-
tively smaller than the other one. It corresponds to a surface
acidity of 0.416 mmol gꢁ1. Whereas, the high temperature peak
indicates the presence of strong acidic sites corresponding
to 1.1 mmol gꢁ1. Thus the total acidity of the material is
1.516 mmol gꢁ1. The Lewis acidity of the transition metals
present at the surface of this porous material could be
responsible for such high surface acidity.
Fig. 5 N2 adsorption/desorption isotherms of the sample at 77 K.
Adsorption points are marked by filled circles and desorption points by
empty circles. Pore size distributions obtained by using NLDFT method
is shown in the inset.
type I (at low P/P0 region) and type IV (at high P/P0 region)
isotherms. Further, this isotherm also shows a mild hysteresis
loop in the pressure region 0.5–0.9 P/P0 of N2, indicating the
presence of large mesopores.46 The BET (Brunauer–Emmett–
Teller) surface area and a pore volume of the porous sample are
233 m2 gꢁ1 and 0.475 cm3 gꢁ1, respectively. The nonlocal
density functional theory (NLDFT) is used to determine the pore
size distribution of the sample (inset of Fig. 6), where two types
of pores: micropore with pore width of 0.94 nm and mesopore
of 6.4 nm are observed. The interparticle porosity of ca. 6.4 nm
could be attributed to the observed mild hysteresis.
Magnetic and hyperne property
The ZFC–FC magnetization curves of the sample at an external
magnetic eld of 500 Oe are shown in Fig. 7. The ZFC magne-
tization remains almost independent of temperature between
300 and 120 K (Tf) and tumbles rapidly on further cooling. The
FC magnetization increases leisurely on cooling and gets almost
saturated below 10 K. The nature of the ZFC–FC curves is far
and away different from those obtained in purely super-
paramagnetic system.9 No signature of superparamagnetic
blocking has been observed up to 300 K. Similar type of
behavior in ZFC–FC magnetization curves has been earlier
Magnetic nanoparticles have an inherent tendency to form
agglomerates. It may be noted that we have adopted a special
Fig. 6 Temperature programmed desorption profile of NH3 of the Fig. 7 ZFC–FC magnetization of the sample at 500 Oe external
sample.
magnetic field.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 78508–78518 | 78513

View Article Online
RSC Advances
Paper
observed for mechanosynthesized Ni0.5Zn0.5Fe2O4,9 Co0.2Zn0.8
-
Fe2O447,48 and ZnFe2O449 nanoparticle systems and explained in
the paradigm of collective magnetic state and spin glass like
behavior.
The sample exhibits clear hysteresis loop at room tempera-
ture (HC ¼ 280 Oe), which indicates that the sample is in
magnetically well ordered state at this temperature (Fig. 8). The
high value of coercive eld has been observed in the M–H curves
(inset of Fig. 8) recorded at lower temperatures (HC ¼ 1200 and
2800 Oe at 100 and 10 K, respectively). The saturation magne-
tization (MSAT) of the sample has been calculated from the M vs.
1/H plot using the law of approach to saturation. The values of
MSAT at 300, 100 and 10 K are 53, 72 and 76 emu gꢁ1, respec-
tively. Moreover, the nonsaturated nature of the magnetization
curve up to 5 T external magnetic eld may be ascribed to the
presence of spin canting in the sample.21
It is well known that the magnetic ordering of the iron
containing materials can be easily investigated with the help of
Fig. 9 Mossbauer spectrum of the sample at 300 K fitted by the
“Lorentzian site analysis” of the Recoil program.
¨
57Fe Mossbauer spectroscopic technique.3,9,16,21,50–55 The
¨
¨
Mossbauer spectrum at 300 K (Fig. 9) has been tted by Lor-
entzian site analysis method of the Recoil program. The
¨
Mossbauer spectrum at 300 K consists of a relaxed sextet magnetization has been recorded in presence of 500 Oe eld.
(76.2%) and a superparamagnetic doublet (23.8%), which The results of ZFC–FC magnetization together with the
¨
suggest that the blocking temperature (TB) of the system is Mossbauer spectroscopic study suggests that 500 Oe eld is
higher than room temperature, most of the particles (72.2%) in enough to align the magnetization vectors of the particles in
the sample exhibit the phenomenon of collective magnetic collective magnetic state.3 As most of the particles in the sample
excitation and the rest are in superparamagnetic state.21 The are in collective magnetic state (72.2%) and dc magnetic
magnetization vector of the particles in collective magnetic state measurement provides the information regarding the magnetic
uctuates very slowly but remains close to easy axis while the character of a sample as a whole, so the contribution coming
magnetization vector of particles in superparamagnetic state from few superparamagnetic particles has been masked in the
ip randomly with faster rate.3 Moreover, it is well known that ZFC–FC magnetizations and M–H measurement. Because of
for system exhibiting superparamagnetic relaxation and this, the ZFC magnetization remains constant in the tempera-
collective magnetic excitation, the outcome of an experiment ture range 120–300 K and the M–H loop at room temperature
depends upon the window time of the measurement technique has displayed hysteresis.9
3
¨
adopted. Due to the lower window time of Mossbauer spec-
The abrupt and rapid fall of ZFC magnetization below 120 K
troscopy (ꢀ10ꢁ7 to 10ꢁ9 s) compared to dc magnetic measure- reveals that the magnetic moments of the particles in the
ment (ꢀ100 s), it succeeded in probing the presence of sample get frozen randomly below this temperature.9 Under
superparamagnetic state in the sample, the signature of which such a situation, the local magnetic order persists and
has not been found in the dc magnetization measurements.16 It Mossbauer spectroscopy, being a sensitive local tool for probing
¨
¨
may be noted that the room temperature Mossbauer spectrum hyperne character, can easily provide the information about
has been recorded without applied magnetic eld while the ZFC such local magnetic order.3,9 In fact the Mossbauer spectrum at
¨
10 K exhibits a clear sextet and gives evidence in favor of the
existence of local magnetic order in the sample (Fig. 1(b)).9 This
result suggests that the thermal uctuation induced relaxation
has been completely wiped out in low temperature and the
system is either in magnetically ordered state as a whole or
there are certain regions in the sample which are magnetically
ordered.3 The abrupt fall of ZFC magnetization below 120 K
discards the possibility of existence of magnetically well ordered
state below this temperature. The low temperature M–H and
¨
Mossbauer spectroscopic studies indicate the presence of spin
canting. Thus by keeping in mind the outcomes of dc magnetic
¨
and Mossbauer study at low temperature, it may be inferred that
the sharp drop of the magnetic moment below Tf in the ZFC
magnetization curve is caused by the random freezing of the
canted surface spins and the cooperative freezing of magnetic
moments exhibiting collective magnetic excitation. In collective
Fig. 8 M–H (hysteresis) loops of the sample at 300, 100 and 10 K.
(inset shows the M–H loops between ꢃ0.3 T for clarity).
78514 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
state, the particles in the system behave like an assembly rather
than an individual one and the anisotropy energy of such an
assembly shows multiminima in phase space.3 This type of
system can display spin glass like freezing behavior below a
certain temperature (Tf) due to cooperative freezing of the
magnetic moments.9 Therefore we propose that the magnetic
moment of the sample drops sharply below 120 K (Tf) as the
core region of the particles in the sample undergoes magnetic
phase transition from collective magnetic state to spin glass like
state through cooperative freezing of spins at the core region
and the random freezing of the spins at the surface due to spin
canting effect. Further, it is true that in spin glass like state the
magnetization falls rapidly but the coercive eld remains
unaffected and due to this the sample displays hysteresis below
120 K.3
Now a days, the industrial applications of ferrite nano-
particles demand stable magnetic order and high magnetiza-
tion at room temperature.9 However, in most of the cases the
unstable spontaneous magnetization at higher temperature in
consequence of superparamagnetism and reduction of
magnetization caused by spin canting severely limit their
Fig. 10 Memory effect in the dc magnetization of the sample (green
line indicates heating cycle and the solid pink circles represent the
cooling cycle).
application possibilities. The dc magnetic study together with magnetic eld of 100 Oe was switched on and the sample was
¨
ineld and without eld Mossbauer spectroscopic study reveal cooled down below 300 K and the magnetization was recorded,
that the sample under investigation is magnetically well (ii) aer reaching at 70 K, the 100 Oe eld was switched off and
ordered at 300 K along with it displays substantial amount of the system was detained in the same state for 1 h and then the
coercive eld (HC ¼ 280 Oe) and this has been noticed only in 100 Oe eld was restored and the sample was cooled down to 50
very few nanometric ferrites.3,9 It may be noted that the high K, (iii) at 50 K, the eld was switched on to 200 Oe and the
energy ball milling has induced large microstrain among the system was arrested at this state for 1 h and then 100 Oe eld
lattice planes, ample amount of grain boundary defect together was restored and the system was cooled down to 25 K, (iv) at 25
with shape and size irregularity which collectively enhance the K, the 100 Oe eld was switched off and the system was main-
stress and surface anisotropy of the system.9 Thus the total tained in that state for 1 h, aer that the 100 Oe eld was
anisotropy energy of the system gets enhanced. The extra restored and the system was cooled down to 10 K, (v) at 10 K, 200
anisotropy contribution due to high energy ball milling has Oe eld was switched on and the system was arrested at this
positive contribution in maintaining stable magnetic order at state for 1 h, then the 100 Oe eld was restored and the system
room temperature and promoting high coercivity.9
was cooled down to 3 K and (vi) nally the system was heated
Moreover, the MSAT at 300 K (53 emu gꢁ1) has been found to be back from 3 K in the presence of 100 Oe magnetic eld and the
the highest among all the reported values of MSATs of mecha- magnetization was recorded. The cooling and heating rate was
nochemically synthesized Ni–Zn ferrite nanoparticles at the same kept constant at 2 K minꢁ1 during the entire measurement
temperature.9 It is well known that the magnetization of nano- period. The recorded magnetization prole has been shown in
metric ferrites depends upon the relative distribution of Fig. 10 which suggests that the heating curve exhibits wiggles at
magnetic cations between tetrahedral (A) and octahedral [B] sites all the points where the eld was switched off and on during
of spinel lattice and the canting angle between [B] site moments. cooling cycle. The memory experiment has revealed that the
In most of the nanometric ferrites magnetization reduces due to sample can remember the temporal and spatial variation of
unfavorable migration of magnetic cations between [B] to (A) site magnetic eld and successfully recollect its past history on
and surface spin disorder or both.3,47,48 In our earlier work on recovering the same temperature. This type of memory effect is
nanosized Ni0.5Zn0.5Fe2O4, we have proposed that the inherent emblematic manifestation of the fact that the sample exhibits
tendency of the reduction of magnetization of nanometric spin glass like slow dynamics at low temperature.9,56–59 The
ferrites due to surface spin canting can be countered by main- presence of collective magnetic state along with frustrated
taining equilibrium cation distribution.9 Even though the present magnetic interaction at the surface region are the underlying
sample exhibits high surface spin canting, it maintains the reason for having slow dynamics and memory behavior in the
equilibrium cation distribution which helps in retaining high sample. It may be noted that for samples exhibiting collective
magnetization in the sample.
magnetic excitation no unique ground state of anisotropy
energy exists but rather the anisotropy energy of the system
shows multiple minima in phase space. For such conguration
of anisotropy energy, the system can approach toward equilib-
Magnetic coding experiment
We have performed the memory experiment (Fig. 10) on the rium but cannot be able to reach it and this leads to spin glass
sample by adopting the following steps: (i) at rst, an external like slow dynamics in the system.60 By tagging the “H drop” as
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 78508–78518 | 78515

View Article Online
RSC Advances
Paper
0 and “H rise” as 1 we can easily store binary number in the reactions with a wide range of substituted aldehydes, methyl
1
sample and same can be recovered back by warming the sample acetoacetate and urea. The products were characterized by H
in a constant magnetic eld. Thus the sample can be used for and 13C NMR.61 The results are listed in Table 4. The yield of the
sensing the spatial and temporal variation of magnetic eld and DHPM products as calculated from the weight ranged ca., 60–
coding, storing and retrieving of binary number through 75% for different aldehydes. When the reaction was carried out
magnetic eld change.
in the absence of any catalyst under similar reaction conditions
no desired product was obtained. This result suggests that this
mechanically activated nanosized Ni/Zn-ferrite is highly reactive
catalyst for this acid catalytic condensation reaction.32
Catalysis
The high surface acidity and BET surface area together with the
magnetic separation potential of the sample have motivated us
to explore its activity as heterogeneous catalyst for the synthesis
Reusability of the catalyst
of 3,4-dihydropyridin-2-1H-(ones) (DHPM) via solvent-free one- Aer separating the used catalyst magnetically, it was washed
pot Biginelli condensation reaction. We have carried out the several times with ethyl acetate and dried in the oven. Further,
Table 4 Biginelli condensation reactions over nanosized Ni/Zn-ferrite catalyst
Entry
Aldehyde
Products
Time (min)
Yield (%)
TOFa (hꢁ1
)
1
10
67
708
2
10
73
771
3
4
10
10
71
65
749
687
5
10
10
66
696
6
No product
—
a
TOF ¼ mol converted/mol of active site/time. Total acidity 1.516 mmol gꢁ1 (obtained from TPD-NH3 analysis).
78516 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
we have reused this catalyst for four consecutive cycles and it
was found that the catalyst was reusable without any signicant
loss of activity. For entry 1 of Table 4, the yield decreased from
67% to 64% aer fourth cycle and in other cases yield did not
change signicantly. Compared to ltration and centrifugation,
the magnetic separation is a simpler and easier procedure
for recovering the catalyst from the reaction mixture with
minimum loss of the catalyst. Thus this magnetically separable
nanosized Ni/Zn-ferrite material has large potential to be used
as heterogeneous catalyst compared to other related non-
magnetic catalysts reported in the literature.
2 R. H. Kodama, A. E. Berkowitz, E. J. McNiff and S. Foner,
Phys. Rev. Lett., 1996, 77, 394.
3 B. Ghosh, S. Kumar, A. Poddar, C. Mazumdar, S. Banerjee,
V. R. Reddy and A. Gupta, J. Appl. Phys., 2010, 108, 034307.
4 B. H. Liu, J. Ding, Z. L. Dong, C. B. Boothroyd, J. H. Yin and
J. B. Yi, Phys. Rev. B: Condens. Matter Mater. Phys., 2006, 74,
184427.
ˇ
´
5 V. Sepelak, A. Feldhoff, P. Heitjans, F. Krumeich, D. Menzel,
F. J. Litterst, I. Bergmann and K. D. Becker, Chem. Mater.,
2006, 18, 3057.
6 C. Cannas, A. Ardu, A. Musinu, D. Peddis and G. Piccaluga,
Chem. Mater., 2008, 20, 6364.
7 C. Pereira, A. M. Pereira, X. Fernandes, M. Rocha, R. Mendes,
Conclusion
´
´
M. P. Fernandez-Garcıa, A. Guedes, P. V. Tavares,
`
´
J. M. Greneche, J. P. Araujo and C. Freire, Chem. Mater.,
The mechano-synthesized nanometric (ꢀ12 nm) Ni0.45Zn0.55
-
2014, 24, 1496.
Fe2O4 possesses good crystalline character and nearly equilib-
rium cation distribution ((Fe3+0.45Zn2+0.55)A[Fe3+1.55 Ni2+0.45]BO4)
and it exhibits stable magnetic order, good amount of coercive
8 B. K. Chatterjee, K. Bhattacharjee, A. Dey, C. K. Ghosh and
K. K. Chattopadhyay, Dalton Trans., 2014, 43, 7930.
9 S. Dey, S. K. Dey, K. Bagani, S. Majumder, A. Roychowdhury,
S. Banerjee, V. R. Reddy and S. Kumar, Appl. Phys. Lett., 2014,
105, 063110.
10 A. Goldman, Modern Ferrite Technology, Van Nostrand,
Reinhold, New York, 1990.
11 K. Vamvakidis, M. Katsikini, D. Sakellari, E. C. Paloura,
O. Kalogirou and C. Dendrinou-Samara, Dalton Trans.,
2014, 43, 12754.
12 S. K. Gore, R. S. Mane, M. Naushad, S. S. Jadhav, M. K. Zate,
Z. A. Alothman and B. K. N. Hui, Dalton Trans., 2015, 44,
6384.
13 M. Menelaou, K. Georgoula, K. Simeonidis and
C. Dendrinou-Samara, Dalton Trans., 2014, 43, 3626.
14 P. Das, A. Dutta, A. Bhaumik and C. Mukhopadhyay, Green
Chem., 2014, 16, 1426.
15 H. J. Cui, J. W. Shi, B. Yuan and M. L. Fu, J. Mater. Chem. A,
2013, 1, 5902.
16 S. Dey, S. K. Dey, B. Ghosh, V. R. Reddy and S. Kumar, Mater.
Chem. Phys., 2013, 138, 833.
eld (280 Oe) and high saturation magnetization (ꢀ53 emu gꢁ1
)
at room temperature. We have shown that the high energy ball
milling induced enhancement of stress and surface anisotropy
helps in retaining stable magnetic order of ferrite nanoparticles
at room temperature and the reduction of magnetization due to
spin canting can be counteracted by tuning the cation distri-
bution in the sample in a favorable manner. These intriguing
magnetic characters of the sample can be successfully used for
the fabrication of magnetic data storage and recording devices
by overcoming the impediments of miniaturization. Further-
more, the sample is able to store the memory of sudden changes
in magnetic eld while cooling and it can reminisce the changes
during heating that can be used in coding, storing and
retrieving of binary number through magnetic eld change. It
can also be used to detect the spatial and temporal variation of
magnetic eld. Further, the sample is highly porous and it
contains both micropores (0.94 nm) and mesopores (6.4 nm).
High catalytic efficiency together with easily recovery of the
magnetic Ni0.45Zn0.55Fe2O4 nanocatalyst for the synthesis of one
pot synthesis of 3,4-dihydropyrimidine-2(1H)-ones (DHPMs)
suggested its further utility as a heterogeneous catalyst in
future.
17 N. Ponpandian, A. Narayanasamy, C. N. Chinnasamy,
`
N. Sivakumar, J. M. Greneche, K. Chattopadhyay,
K. Shinoda, B. Jeyadevan and K. Tohji, Appl. Phys. Lett.,
2005, 86, 192510.
18 M. Jalaly, M. H. Enayati, P. Kameli and F. Karimzadeh,
Physica B: Condensed Matter, 2010, 405, 507.
19 S. Verma, P. A. Joy and S. Kurian, J. Alloys Compd., 2011, 509,
8999.
Acknowledgements
One of the authors (SD) gratefully acknowledges the nancial
support of Jadavpur University for providing research fellow-
ship. RG acknowledges CSIR, New Delhi for a senior research
fellowship. The UPE program of UGC and the PURSE program
of DST, Govt. of India are also acknowledged. We are thankful to
UGC-DAE CSR, Indore Center for ineld Mossbauer measure-
ment. We also gratefully acknowledge Prof. R. N. Joarder (Retd.)
for helpful discussion.
20 N. Sivakumar, A. Narayanasamy, N. Ponpandian,
`
J. M. Greneche, K. Shinoda, B. Jeyadevan and K. Tohji, J.
Phys. D: Appl. Phys., 2006, 39, 4688.
21 S. Dey, S. K. Dey, B. Ghosh, P. Dasgupta, A. Poddar,
V. R. Reddy and S. Kumar, J. Appl. Phys., 2013, 114, 093901.
22 M. Kooti and M. Afshari, Sci. Iran., 2012, 19(6), 1991.
23 Q. Wan, P. Li, J. Shan, F. Zhai, Z. Li and X. Qu, J. Phys. Chem.
C, 2015, 119, 2925.
¨
24 T. Liu, L. Wang, P. Yang and B. Hu, Mater. Lett., 2008, 62,
4056.
Notes and references
1 J. L. Dormann and M. Nogues, J. Phys.: Condens. Matter, 1990, 25 K. Yan, X. Wu, X. An and X. Xie, J. Alloys Compd., 2013, 552,
2, 1223.
405.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 78508–78518 | 78517

View Article Online
RSC Advances
Paper
26 N. Velinov, K. Koleva, T. Tsoncheva, E. Manova, D. Paneva, 51 S. Bid, A. Banerjee, S. Kumar, S. K. Pradhan, U. De and
K. Tenchev, B. Kunev and I. Mitov, Catal. Commun., 2013,
32, 41.
D. Banerjee, J. Alloys Compd., 2001, 326, 292.
´
52 G. F. Goya, T. S. Berquo, F. C. Fonseca and M. P. Morales, J.
27 C. Singh, A. Goyal and S. Singhal, Nanoscale, 2014, 6, 7959.
Appl. Phys., 2003, 94, 3520.
28 Y. L. N. Murthy, B. S. Diwakar, B. Govindh, K. Nagalakshmi, 53 C. R. Alves, R. Aquino, J. Depeyrot, T. A. P. Cotta,
I. V. K. Viswanath and R. Singh, J. Chem. Sci., 2012, 124, 639.
29 A. M. Kulkarni, U. V. Desai, K. S. Pandit, M. A. Kulkarni and
P. P. Wadgaonkar, RSC Adv., 2014, 4, 36702.
30 C. O. Kappe, Acc. Chem. Res., 2000, 33, 879.
31 J. Azizian, A. A. Mohammadi, A. R. Karimi and
M. R. Mohammadizadeh, Appl. Catal., A, 2006, 300, 85.
32 M. Pramanik and A. Bhaumik, ACS Appl. Mater. Interfaces,
2014, 6, 933.
M. H. Sousa, F. A. Tourinho, H. R. Rechenberg and
G. F. Goya, J. Appl. Phys., 2006, 99, 08M905.
54 C. Cannas, A. Musinu, G. Piccaluga, D. Fiorani, D. Peddis,
H. K. Rasmussen and S. M4rup, J. Chem. Phys., 2006, 125,
164714.
55 K. He, C. Y. Xu, L. Zhen and W. Z. Shao, Mater. Lett., 2008, 62,
739.
56 S. Chakraverty, B. Ghosh, S. Kumar and A. Frydman, Appl.
Phys. Lett., 2006, 88, 042501.
33 J. Mondal, T. Sen and A. Bhaumik, Dalton Trans., 2012, 41,
6173.
57 Y. Sun, M. B. Salamon, K. Garnier and R. S. Averback, Phys.
Rev. Lett., 2003, 91, 167206.
¨
34 K. Lagarec and D. G. Rancourt, Recoil-Mossbauer Spectral
¨
Analysis Soware for Window, University of Ottawa Press. 58 M. Sasaki, P. E. Jonsson, H. Takayama and H. Mamiya, Phys.
Ottawa, 1998. Rev. B: Condens. Matter Mater. Phys., 2005, 71, 104405.
35 T. A. Anh4j, B. Bilenberg, B. Thomsen, C. D. Damsgaard, 59 S. Chakraverty, M. Bandyopadhyay, S. Chatterjee,
H. K. Rasmussen, C. S. Jacobsen, J. Mygind and S. M4rup,
J. Magn. Magn. Mater., 2003, 260, 115.
S. Dattagupta, A. Frydman, S. Sengupta and P. A. Sreeram,
Phys. Rev. B: Condens. Matter Mater. Phys., 2005, 71, 054401.
36 A. Altomare, C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, 60 M. Bandyopadhyay and S. Dattagupta, Phys. Rev. B: Condens.
R. Rizzi and E. J. Werner, J. Appl. Crystallogr., 2000, 33, 1180. Matter Mater. Phys., 2006, 74, 214410.
37 P. E. Werner, L. Eriksson and M. J. Westdahl, J. Appl. 61 H and 13C NMR data of some of the condensation products
1
Crystallogr., 1985, 18, 367.
reported in Table 4. 5-Methoxycarbonyl-4-phenyl-6-methyl-
3,4-dihydropyridin-2(1H)-one (entry 1). H NMR (DMSO-d6,
1
38 A. Boultif and D. Louer, J. Appl. Crystallogr., 2004, 37, 724.
39 A. Altomare, R. Caliandro, M. Camalli, C. Cuocci,
C. Giacovazzo, A. G. G. Moliterni and R. Rizzi, J. Appl.
Crystallogr., 2004, 37, 1025.
40 L. Lutterotti, MAUDWEB, Version 1.9992, 2004.
41 S. Dey, S. K. Dey, S. Majumder, A. Poddar, P. Dasgupta,
S. Banerjee and S. Kumar, Physica B: Condensed Matter,
2014, 448, 247.
500 MHz): d (ppm): 9.17 (s, 1H), 7.71 (s, 1H), 7.18–7.30
(m, 5H), 5.10 (d, J ¼ 3 Hz, 1H), 3.50 (s, 3H), 2.22 (s, 3H);
13C NMR (DMSO-d6, 125 MHz): d (ppm): 166.4, 152.7,
149.2, 145.3, 129.0, 127.8, 126.7, 99.6, 54.4, 51.3,
18.4. 5-Methoxycarbonyl-4-(4-bromophenyl)-6-methyl-3,4-
1
dihydropyridin-2(1H)-one (entry 2). H NMR (DMSO-d6, 500
MHz): d (ppm): 9.26 (s, 1H), 7.78 (s, 1H), 7.51 (d, J ¼ 8.5
Hz, 2H), 7.17 (d, J ¼ 8.5 Hz, 2H), 5.12 (d, J ¼ 2.5 Hz, 1H),
3.52 (s, 3H), 2.24 (s, 3H); 13C NMR (DMSO-d6, 125 MHz): d
(ppm): 166.3, 152.5, 149.5, 144.6, 131.9, 129.0, 120.9, 99.1,
53.9, 51.4, 18.4. 5-Methoxycarbonyl-4-(4-hydroxyphenyl)-6-
methyl-3,4-dihydropyridin-2(1H)-one (entry 3). 1H NMR
(DMSO-d6, 500 MHz): d (ppm): 9.31 (s, 1H), 9.10 (s, 1H),
7.60 (s, 1H), 7.01 (d, J ¼ 8Hz, 2H), 6.67 (d, J ¼ 8.5 Hz, 2H),
5.02 (s, 1H), 3.51 (s, 3H), 2.21 (s, 3H); 13C NMR (DMSO-d6,
125 MHz): d (ppm): 166.4, 157.0, 152.7, 148.5, 135.7, 127.8,
115.5, 99.9, 53.7, 51.2, 18.3. 5-Methoxycarbonyl-4-(2-
nitrophenyl)-6-methyl-3,4-dihydropyridin-2(1H)-one (entry
4). 1H NMR (DMSO-d6, 500 MHz): d (ppm): 9.36 (s, 1H),
8.12–8.10(m, 2H), 7.90 (s, 1H), 7.65–7.60 (m, 2H), 5.28 (d, J
¼ 3 Hz, 1H), 3.52 (s, 3H), 2.26 (s, 3H). 5-Methoxycarbonyl-
6-methyl-4-styryl-3,4-dihydropyrimidin-2(1H)-one (entry 5).
1H NMR (DMSO-d6, 500 MHz): d (ppm): 9.15 (s, 1H,), 7.54
(1H, s), 7.23–7.40 (m, 5H), 6.36 (d, J ¼ 15 Hz, 1H), 6.21
(dd, J ¼ 6 Hz, 16 Hz, 1H), 4.72 (d, J ¼ 3 Hz, 1H), 3.61 (s,
3H), 2.18 (s, 3H); 13C NMR (DMSO-d6, 125 MHz,): d (ppm):
165.6, 152.6, 148.6, 136.2, 130.0, 128.6, 127.9, 127.5, 126.3,
97.6, 51.7, 50.8, 17.7, 14.2.
42 S. Majumder, S. Dey, K. Bagani, S. K. Dey, S. Banerjee and
S. Kumar, Dalton Trans., 2015, 44, 7190.
43 A. C. Larson and R. B. von Dreele, General structure analysis
system (GSAS), Report LAUR, Los Alamos National
Laboratory, 2000, pp. 86–748.
44 B. H. Toby, J. Appl. Crystallogr., 2001, 34, 210.
¨
˘
¨
¨
45 Y. Koseoglu, A. Baykal, F. Gozuak and H. Kavas, Polyhedron,
2009, 28, 2887.
46 S. Dutta, S. De, A. K. Patra, M. Sasidharan, A. Bhaumik and
B. Saha, Appl. Catal., A, 2011, 409–410, 133.
47 R. N. Bhowmik, R. Ranganathan, R. Nagarajan, B. Ghosh
and S. Kumar, Phys. Rev. B: Condens. Matter Mater. Phys.,
2005, 72, 094405.
48 R. N. Bhowmik, R. Ranganathan, S. Sarkar, C. Bansal and
R. Nagarajan, Phys. Rev. B: Condens. Matter Mater. Phys.,
2003, 68, 134433.
49 C. N. Chinnasamy, A. Narayanasamy, N. Ponpandian,
´
K. Chattopadhyay, H. Gueralt and J. M. Greneche, J. Phys.:
Condens. Matter, 2000, 12, 7795.
50 B. Ghosh and S. Kumar, Hyperne Interact., 2008, 183, 163.
78518 | RSC Adv., 2015, 5, 78508–78518
This journal is © The Royal Society of Chemistry 2015