Doping effect of nonmagnetic impurity on the spin-Peierls-like transition in the quasi-one-dimensional (quasi-1D) spin system of 1-(4′-nitrobenzyl)pyridinium bis(maleonitriledithiolato)nickelate

Article abstract of DOI:10.1016/j.poly.2009.02.008

A nonmagnetic compound, [NO₂BzPy][Cu(mnt)₂] (mnt^2- = maleonitriledithiolate; NO₂BzPy⁺ = 1-(4′-nitrobenzyl)pyridinium), is isostructural with [NO₂BzPy][Ni(mnt)₂], which is a quasi

Full text of DOI:10.1016/j.poly.2009.02.008

Polyhedron 28 (2009) 2075–2079
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Doping effect of nonmagnetic impurity on the spin-Peierls-like transition in
the quasi-one-dimensional (quasi-1D) spin system of 1-(40-nitrobenzyl)pyridinium
bis(maleonitriledithiolato)nickelate
a
a
c
c
Xiao-Ming Ren a,b, , Guang-Xiang Liu , Heng Xu , Tomoyuki Akutagawa , Takayoshi Nakamura
*
a Provincial Key Lab of Anhui for Coordination Compounds, Anqing Normal College, Anqing 246011, PR China
b College of Science, Nanjing University of Technology, Nanjing 210009, PR China
c Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 20 February 2009
A
nonmagnetic compound, [NO2BzPy][Cu(mnt)2] (mnt2ꢀ = maleonitriledithiolate; NO2BzPy+ = 1-(40-
nitrobenzyl)pyridinium), is isostructural with [NO2BzPy][Ni(mnt)2], which is a quasi-1D spin system
and exhibits a spin-Peierls-like transition with J = 192 K in the gapless state and spin energy gap = 738 K
in the dimerization state, respectively. Further, five nonmagnetic impurity doped compounds [NO2Bz-
Py][CuxNi1ꢀx(mnt)2] (x = 0.04–0.74) were prepared, and their crystal structures as well as magnetic prop-
erties were investigated. The nonmagnetic doping causes the suppression of the spin transition with an
average rate of 139(13) K/percentage of dopant concentration, and the transition collapse is estimated at
around x > 0.5.
Keywords:
Bis(maleonitriledithiolato)nickelate
Spin-Peierls-like transition
Nonmagnetic doping
Magnetic property
Crystal structure
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
nature is antiferromagnetic (AFM) above transition temperature,
while below that a spin gap is opened with the spin chain dimer-
Impurity doping of a low-dimensional magnetic system often
results in non-intuitive ground states and transition behavior dif-
fering from that of the parent material [1–7]. Lots of investigations
for doping magnetic impurity with different spins have been done
theoretically and experimentally for the low-dimensional inor-
ganic magnetic systems since the first inorganic spin-Peierls com-
pound CuGeO3 was discovered [1–8]. In contrast, the examples of
an impurity doping on the low-dimensional molecular magnetic
system are very rare [9–12] even if the molecular spin-Peierls tran-
sition compounds have been known much earlier than the
inorganic one [13–15]. One of crucial reasons to cause the above-
mentioned situation is that the molecular structure is usually so
complicated that it is not easy to find a suitable dopant that match
with the parent material in both molecular structure and valence.
In our previous study, we observed a peculiar spin-Peierls-like
transition in 1-(40-nitrobenzyl)pyridinium bis(maleonitriledithio-
lato)nickelate (Scheme 1 and abbreviated as [NO2BzPy][Ni(mnt)2])
[12]. This compound possesses columnar stacks along c-axis with
cations and anions segregated, and the regular anionic stack can
be considered as a uniform magnetic chain with S = 1/2 since the
[Ni(mnt)2]ꢀ monoanion bears a half spin. The magnetic exchange
ization [16]. Instead of [Ni(mnt)2]ꢀ monoanion with nonmagnetic
[Au(mnt)2]ꢀ monoanion, the compound of [NO2BzPy][Au(mnt)2],
which is isostructural with [NO2BzPy][Ni(mnt)2], was obtained,
and the effect of nonmagnetic [NO2BzPy][Au(mnt)2] doping in
the lattice of [NO2BzPy][Ni(mnt)2] on the spin-Peierls-type transi-
tion was further investigated [17]. The doped systems
[NO2BzPy][AuxNi1ꢀx(mnt)2] exhibit that: (1) within an anionic
stack, [Au(mnt)2]ꢀ substituting [Ni(mnt)2]ꢀ does not change the
crystal structure of [Ni(mnt)2]ꢀ compound, moreover, the
[Ni(mnt)2]ꢀ and [Au(mnt)2]ꢀ anions could not be distinguished
from the single-crystal structure temperatures above 10 K; (2)
even though an anionic stack exhibits a disordered structural fea-
ture, the magnetic behavior does not show a random spin system
characteristic in the heavier doped system (x P 0.49), additionally,
the fits for temperature dependence of magnetic susceptibility
indicated the presence of stronger AFM coupling interaction be-
tween the [Ni(mnt)2]ꢀ anions which are separated by the nonmag-
netic [Au(mnt)2]ꢀ species; (3) the transition is suppressed by
nonmagnetic doping and collapsed at around x > 0.27, and in a
heavier doped system with x = 0.49, the spin gap vanishes and a
gapless phase is achieved again, and this magnetic behavior
resembles to the phenomena observed in inorganic spin-Peierls
transition systems such as CuGO3 [1–3] and TlCuCl3 [4], however,
the transition collapses when x value is much higher than those
found in the inorganic spin-Peierls transition systems and (4)
single-crystal EPR measurements and theoretical analysis for the
* Corresponding author. Address: Provincial Key Lab of Anhui for Coordination
Compounds, Anqing Normal College, Anqing 246011, PR China. Tel./fax: +86 556
5500090.
E-mail address: xmren@njut.edu.cn (X.-M. Ren).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.02.008

2076
X.-M. Ren et al. / Polyhedron 28 (2009) 2075–2079
\S—M—S bite angles: \S—Au—S ¼ 90:50ꢁ, \S—Cu—S ¼ 92:37ꢁ
and \S—Ni—S ¼ 92:44ꢁ in above-mentioned three compounds).
In this contribution, we further investigate the crystal structures
and magnetic properties of a series of compounds with a formula
[NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–1 and it represents the molar
fraction of Cu in a doped system).
2. Experimental
2.1. Preparation of compounds
[NO2BzPy][Ni(mnt)2] and [NO2BzPy]2[Cu(mnt)2] were prepared
according to the published procedures [16,19].
[NO2BzPy][Cu(mnt)2]: The compound [NO2BzPy]2[Cu(mnt)2] was
oxidized by 0.75 equivalent of I2 to afford [NO2BzPy][Cu(mnt)2]
(yield: ꢂ72%). Single crystals suitable for X-ray structural analysis
were obtained by diffusing diethyl ether into an acetonitrile
solution of [NO2BzPy][Cu(mnt)2]. Elemental Anal. Calc. for
C20H11N6O2S4Cu: C, 43.0; H, 1.98; N, 15.0%. Found: C, 42.8; H,
2.04; N, 14.9%.
[NO2BzPy][CuxNi1ꢀx(mnt)2]: Each doped compound was prepared
according to the procedure employed in the literature [17], and the
product is needle- or block-shaped crystals which are suitable for
X-ray structural analysis. The molar ratio of [NO2BzPy][Ni(mnt)2]
to [NO2BzPy][Cu(mnt)2] in the starting materials and the results
of elemental analyses for C, H and N for [NO2BzPy][CuxNi1ꢀ
x(mnt)2] (x = 0.04–0.74) are presented in Table 1.
Scheme 1.
sample of [NO2BzPy][Au0.57Ni0.43(mnt)2] disclosed the existence of
intermolecular charge transfer between the adjacent [Ni(mnt)2]ꢀ
and [Au(mnt)2]ꢀ species in an anionic stack [18].
It is well known that the structural feature of a nonmagnetic
dopant strongly influence the magnetic transition behavior in a
spin-Peierls system, this very important theme forms the
background of the present work. The nonmagnetic compound
[NO2BzPy][Cu(mnt)2] is isostructural with the nonmagnetic
compound [NO2BzPy][Au(mnt)2] as well as the spin-Peierls-
like transition compound [NO2BzPy][Ni(mnt)2], compared with
[NO2BzPy][Au(mnt)2], the molecular geometric parameters in
[Cu(mnt)2]ꢀ species are much closer to those in [Ni(mnt)2]ꢀ anion
2.2. Physical measurements
Elemental analyses were performed with a Perkin–Elmer 240
analytical instrument. IR spectra were recorded on Bruker Vector
22 spectrophotometer (KBr disc). The molar ratio of Ni-to-Cu for
each alloy compound was determined by inductively coupled plas-
ma-atomic emission spectrometer (ICP-AES, Atomscan Advantage,
USA). Magnetic susceptibility measurement over the range of 2–
350 K for each polycrystalline sample was carried out using a
Quantum Design MPMS-XL superconducting quantum interference
device (SQUID) magnetometer under 1.0 T.
than [Au(mnt)2]ꢀ species (the averaged M–S distances: dAu–S
2.3085, dCu–S = 2.1886 and dNi–S = 2.1466 Å; and the averaged
=
Table 1
Elemental analyses (C, H and N), molar ratio of [Cu(mnt)2]ꢀ to [Ni(mnt)2]ꢀ in the
starting materials and the occupation factor of Cu(Ni) in the final crystal structural
refinement for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0.04–0.74).
Calculated
Found
C
Cu:Nia
Cu:Nib
2.3. X-ray structural analyses
C
H
N
H
N
x = 0.04
x = 0.12
x = 0.32
x = 0.50
x = 0.74
43.3
43.3
43.2
43.1
43.1
2.00
2.00
1.99
1.99
1.99
15.2
15.1
15.1
15.1
15.1
43.1
43.0
43.4
43.1
42.8
2.05
2.03
2.06
2.02
2.00
15.0
14.9
14.8
15.2
15.3
0.05:0.95
0.10:0.90
0.33:0.67
0.49:0.51
0.75:0.25
0.04:0.96
0.12:0.88
0.32:0.68
0.50:0.50
0.74:0.26
Crystallographic data were collected using a Rigaku Raxis-Rapid
diffractometer with Mo
Ka (k = 0.71073 Å) radiation from a
graphite monochromator. Structures were solved by direct method
using the SHELXL-97 software package [20]. The non-hydrogen
atoms were refined anisotropically using the full-matrix least-
squares method on F2. It is similar to the [NO2BzPy]-[AuxNi
a
The molar ratio in the starting materials.
The results from ICP measurements.
b
Table 2
Crystallographic data for [NO2BzPy][CuxNi1ꢀx(mnt)2] with molecular formula of C20H11CuxNi1ꢀxN6O2S4 at 293 K.
x = 0.04
x = 0.12
x = 0.32
x = 0.50
x = 0.74
x = 1
CCDC no.
Molecular mass
Space group
a (Å)
b (Å)
c (Å)
705213
554.49
P2(1)/c
12.192(2)
26.543(5)
7.2383(14)
102.82(3)
2284.0(8), 4
1.251
705214
554.88
P2(1)/c
12.194(2)
26.546(5)
7.2556(15)
102.94(3)
2289.0(8), 4
1.257
705215
555.84
P2(1)/c
12.198(2)
26.516(5)
7.2511(15)
102.97(3)
2285.4(8), 4
1.280
705216
556.71
P2(1)/c
12.152(2)
26.448(5)
7.2930(15)
103.15(3)
2282.6(8), 4
1.301
705217
557.87
P2(1)/c
12.180(2)
26.479(5)
7.3027(15)
103.19(3)
2293.1(8), 4
1.320
705212
559.13
P2(1)/c
12.217(2)
26.559(5)
7.3433(15)
103.42(3)
2317.6(8), 4
1.334
b (°)
V (Å3), Z
l
(mmꢀ1
)
k (Å)
q
0.71073
1.613
0.71073
1.610
0.71073
1.615
0.71073
1.620
0.71073
1.616
0.71073
1.602
(g cmꢀ3
)
R1
0.0331
0.0288
0.0572
0.1138
0.0439
0.0419
wR2
0.0817
0.0647
0.1100
0.3746
0.1271
0.0699
P
P
P
P
R1
=
(||Fo| ꢀ |Fc||)/ |Fo|, wR2
=
w(|Fo|2 ꢀ |Fc|2)2/ w(|Fo|2)2]1/2
.

X.-M. Ren et al. / Polyhedron 28 (2009) 2075–2079
2077
1ꢀx(mnt)2] compounds that the [Cu(mnt)2]ꢀ anions distribute ran-
domly in the [Ni(mnt)2]ꢀ stack for all doped crystals of [NO2BzPy][-
CuxNi1ꢀx(mnt)2] at 293 K, and the occupancy factors of Cu and Ni
atoms for each doped sample were defined by ICP measurement.
All hydrogen atoms were placed at calculated positions (C–
H = 0.930 Å for benzene or pyridine rings and 0.970 Å for methy-
lene) and refined riding on the parent atoms with U(H) = 1.2 ꢃ Ueq
(bonded C atom). Details of the lattice parameters, data collections,
and refinements for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0.04–1) at
293 K are summarized in Table 2.
3. Results and discussion
3.1. Description of crystal structures
Crystal structure of [NO2BzPy][Cu(mnt)2] at 293 K: This
compound crystallizes in monoclinic space group P2(1)/c, and it
is isostructural with the compounds [NO2BzPy][Ni(mnt)2] and
[NO2BzPy][Au(mnt)2]. The asymmetric unit in a cell is comprised
of a coupled of [Cu(mnt)2]ꢀ and NO2BzPy+. The [Cu(mnt)2]ꢀ anion
possesses roughly a planar geometry (Fig. 1a), and the Cu–S
lengths range from 2.1844(8) to 2.1982(8) Å, these values are close
to the Ni–S lengths [2.1409(7)–2.1565(6) Å] in [NO2BzPy]-
[Ni(mnt)2], and shorter than the Au–S lengths [2.303(2)–
2.3153(19) Å] in [NO2BzPy][Au(mnt)2]. The S–Cu–S bite angles of
92.08(3)° and 92.66(3)° are also close to the S–Ni–S values
Fig. 2. (a) Distances of MꢄꢄꢄM (d1 and d2) and interplane between neighboring
anions (h1 and h2) and (b) central-to-central distance between adjacent benzene
rings (c1 and c2).
[92.32(3)° and 92.56(3)°] in [NO2BzPy][Ni(mnt)2]. The molecular
conformation of [NO2BzPy]+ cation in [Cu(mnt)2]ꢀ compound
resembles to that in [Ni(mnt)2]ꢀ compound. For example, the dihe-
dral angles of pyridine ring and benzene ring with the reference
plane CAr–CH2–NPy are 88.3° and 64.8° in [Cu(mnt)2]ꢀ compound
versus 86.9° and 65.2° in [Ni(mnt)2]ꢀ compound, respectively.
The pyridine and benzene rings makes a dihedral angle of 90.2°
in [NO2BzPy][Cu(mnt)2] and 95.0° in [NO2BzPy][Ni(mnt)2].
Both anions and cations form, respectively, the segregated
stacks that run parallel to c-axis (Fig. 1b). Within anionic stacks,
the face-to-face anions slid along b-axis and eclipse each other.
The interplane distances between the adjacent [Cu(mnt)2]ꢀ anions,
which is defined by four coordinated S atoms, are h1 = 3.507 and
h2 = 3.493 Å (Fig. 2a), while the adjacent CuꢄꢄꢄCu distances are ex-
actly identical with d1 = d2 = 3.895 Å. The cationic stack is also reg-
ular with a uniform central-to-central distance of 4.280 Å between
neighboring benzene rings (cf. Fig. 2b).
Crystal structures of [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0.04–0.74) at
293 K: As shown in Table 2, each compound with formula
[NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0.04–0.74) is isostructural to the
parent compounds with very similar lattice parameters. The M–S
lengths and S–M–S bite angles along with their estimated standard
deviations are presented in Table 3. With the doping concentration
x increases, the distances of MꢄꢄꢄM, MꢄꢄꢄS, SꢄꢄꢄS and interplanar dis-
tances between the nearest neighbors (h1, h2 refer to Fig. 2a) within
an anionic stack change gradually and monotonically (cf. Fig. 3),
and this characteristic of structural variation is distinct from the
[NO2BzPy][AuxNi1ꢀx(mnt)2] systems.
3.2. Magnetic susceptibilities
The magnetic behavior of each [NO2BzPy][CuxNi1ꢀx(mnt)2]
(x = 0–1) was determined on its polycrystalline sample from 2 to
350 K. These compounds are isostructural with each other. There-
fore, it is reasonable to suppose that the diamagnetism for each
compound of [NO2BzPy][CuxNi1ꢀx(mnt)2] is equal roughly to the
magnetic susceptibility of [NO2BzPy][Cu(mnt)2]. The corrected
Fig. 1. (a) ORTEP view with displacement ellipsoids at 50% possibility level and (b)
packing diagram of [NO2BzPy][Cu(mnt)2] projected along c-axis.

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X.-M. Ren et al. / Polyhedron 28 (2009) 2075–2079
Table 3
The coordinated bond lengths (Å) and angles (°) in an anionic moiety for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–1).
x = 0
x = 0.04
x = 0.12
x = 0.32
x = 0.50
x = 0.74
x = 1
M–S1
M–S2
M–S3
M–S4
S1–M–S2
S3–M–S4
2.1409(7)
2.1442(6)
2.1446(7)
2.1565(6)
92.32(3)
92.56(3)
2.1418(9)
2.1443(9)
2.1450(9)
2.1555(8)
92.22(4)
92.48(4)
2.1452(7)
2.1488(6)
2.1511(7)
2.1611(6)
92.16(3)
92.43(3)
2.1426(12)
2.1451(12)
2.1481(12)
2.1562(12)
92.26(5)
2.158(4)
2.160(4)
2.162(4)
2.180(4)
92.15(15)
92.56(15)
2.1647(9)
2.1649(8)
2.1668(9)
2.1757(8)
92.16(4)
92.62(3)
2.1844(8)
2.1844(9)
2.1872(9)
2.1982(8)
92.08(3)
92.51(5)
92.66(3)
Fig. 3. Variations of interatomic and interplane distances between neighboring
anions in a stack (h1 and h2; see Fig. 2) as x for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–
0.74) at 293 K and [NO2BzPy][Ni(mnt)2] at 273 K [16].
molar paramagnetic susceptibilities of [NO2BzPy][CuxNi1ꢀx(mnt)2]
(x = 0–0.74) as well as the nonmagnetic compound of [NO2BzPy][-
Cu(mnt)2] are given in Fig. 4 as
vm = f(T), from which it can be
found that the nonmagnetic compound of [NO2BzPy][Cu(mnt)2]
clearly shows diamagnetism behavior (with negative magnetic
susceptibilities).
For the parent compound of [NO2BzPy][Ni(mnt)2] (x = 0), as
reported in our previous work [16], a magnetic transition occurs
around 181 K, and the phenomenology of the magnetic transition
closely resembles that of a spin-Peierls transition. The spin gap
with the value of 738 K in dimerized state was estimated from
the fits of the magnetic susceptibility data in low temperature
phase, and the magnetic exchange interaction with J/kB =
192(3) K [17] in high temperature phase was evaluated from the
analysis for magnetic susceptibility data utilizing a regular antifer-
romagnetic Heisenberg model for a S = ½ linear chain system [21].
As displayed in Fig. 4a and b, the nonmagnetic doping causes (1)
the molar magnetic susceptibility decreasing with x value increase
when x < 0.5; (2) an onset of a strong paramagnetic background in
the low temperature region and (3) a damping of the spin transi-
tion. These behaviors are similar to the doped systems of
[NO2BzPy][AuxNi1ꢀx(mnt)2] [17]. It is understandable that the non-
magnetic doping induces the strong paramagnetic background in
the low temperature region for the doped sample since the antifer-
romagnetic spin chains of [Ni(mnt)2]ꢀ are broken at the position of
Fig. 4. Plots of
temperature range of (a) 70–350 K and (b) 2–80 K.
vm(T) versus T for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–1) in the
nonmagnetic dopants [Cu(mnt)2]ꢀ, moreover, the spin number in a
chain should be randomly even and odd in equal probability.
Therefore, the spin at the end of any odd numbered spin chain be-
comes uncoupled, giving a contribution to the paramagnetic sus-
ceptibility, and this contribution is dominant especially for
heavily doped systems. In the doped system at x = 0.5, the broad
maximum of magnetic susceptibility appears in the
which is a typical characteristic of a lowered dimensionality of spin
system due to the existence of short-range ordering. It is
vm–T plot

X.-M. Ren et al. / Polyhedron 28 (2009) 2075–2079
2079
[CuxNi1ꢀx(mnt)2] (x = 0.04–0.74), and investigated the nonmagnetic
impurities effects on the spin-Peierls-like transition in a quasi-1D
spin system of [NO2BzPy][Ni(mnt)2]. The nonmagnetic impurities
suppress the spin-Peierls-like transition, and the transition temper-
ature TC reduces at an average rate of 139(13) K/percentage of non-
magnetic dopant. The transitioncollapse is estimated around x > 0.5.
Compared with the [NO2BzPy][AuxNi1ꢀx(mnt)2] system, the
[NO2BzPy][CuxNi1ꢀx(mnt)2] system shows higher x values of the
transition collapsing and smaller x dependence of TC shift, and these
differences may be originate from the molecular structure distinc-
tion between [Cu(mnt)2]ꢀ and [Au(mnt)2]ꢀ anions, for example,
the average Au–S length is around 0.15 Å longer than the average
Ni–S length whereas the average Cu–S length is similar to the Ni–S
distance.
Supplementary data
CCDC 705212–705217 contain the supplementary crystallo-
graphic data for each compound of [NO2BzPy][CuxNi1ꢀx(mnt)2]
(x = 0.04–1). These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgments
X.M. Ren thanks the Natural Science Foundation for Outstand-
ing Scholars of Anhui Province, PR China (Grant Nos. 044-J-04011
and 2005hbz20).
References
[1] M. Hase, I. Terasaki, Y. Sasago, K. Uchinokura, Phys. Rev. Lett. 71 (1993) 4059.
[2] S.B. Oseroff, S.W. Cheong, B. Aktas, M.F. Hundley, Z. Fisk, L.W. Rupp Jr., Phys.
Rev. Lett. 74 (1995) 1450.
[3] T. Masuda, A. Fujioka, Y. Uchiyama, I. Tsukada, K. Uchinokura, Phys. Rev. Lett.
80 (1998) 4566.
[4] A. Osawa, T. Ono, H. Tanaka, Phys. Rev. B 66 (2002) 020405.
[5] M. Isobe, Y. Ueda, J. Mag. Mag. Mater. 177–181 (1998) 671.
[6] M. Lohmann, H.-A. Krug von Nidda, A. Loidl, E. Morré, M. Dischner, C. Geibel,
Phys. Rev. B 61 (2000) 9523.
Fig. 5. (a) Plots of d(vmT)/dT versus T for [NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–0.5) and
(b) the x dependences of TC.
noteworthy that the transition is still observed with the vm value
[7] T. Otsuka, M. Yoshimaru, K. Awaga, H. Imai, T. Inabe, N. Wada, M. Ogata, J. Phys.
Soc. Jpn. 70 (2001) 2711.
clear dropping in the
v
m–T plot even if the change is small. In
the heavily doped system of x = 0.74, the shape of
v
m(T)–T plot is
[8] V.N. Glazkov, A.I. Smirnov, H.-A. Krug von Nidda, A. Loidl, K. Uchinokura, T.
Masuda, Phys. Rev. Lett. 94 (2005) 057205.
[9] M. Mito, S. Tanaka, T. Kawae, K. Takeda, M. Yanagimoto, K. Mukai, Physica B
329–333 (2003) 1150.
[10] K. Mukai, K. Suzuki, K. Ohara, J.B. Jamali, N. Achiwa, J. Phys. Soc. Jpn. 68 (1999)
3078.
[11] K. Mukai, Y. Shimobe, J.B. Jamali, N. Achiwa, J. Phys. Chem. B 103 (1999) 10876.
[12] X. Ribas, A. Sironi, N. Masciocchi, E.B. Lopes, M. Almeida, J. Veciana, C. Rovira,
Inorg. Chem. 44 (2005) 2358.
[13] J.W. Bray Jr., H.R. Hart, L.V. Interrante, I.S. Jacobs, J.S. Kasper, G.D. Watkins, S.H.
Wee, J.C. Bonner, Phys. Rev. Lett. 35 (1975) 744.
[14] I.S. Jacobs, J.W. Bray Jr., H.R. Hart, L.V. Interrante, J.S. Kasper, G.D. Watkins, D.E.
Prober, J.C. Bonner, Phys. Rev. B 14 (1976) 3036.
totally different from other doped systems, in which the typical
characteristic of a lowered dimensionality of spin system (with a
broad maximum of magnetic susceptibility) and the magnetic
transition disappear, and the temperature dependences of mag-
netic susceptibility exhibits
Fig. 5a depicts the derivative curves of
a
simple Curie–Weiss behavior.
mT versus for
v
T
[NO2BzPy][CuxNi1ꢀx(mnt)2] (x = 0–0.5) and Fig. 5b plots the
corresponding x dependences of TC, which is defined as the peak
temperature in the d(vmT)/dT–T plot. The values of TC(x) reduce lin-
[15] S. Huizinga, J. Kommandeur, G.A. Sawatzky, B.T. Thole, K. Kopinga, W.J.M. de
Jonge, J. Roos, Phys. Rev. B 19 (1979) 4723.
[16] X.M. Ren, Q.J. Meng, Y. Song, C.J. Hu, C.S. Lu, X.Y. Chen, Inorg. Chem. 41 (2002)
5686.
[17] X.M. Ren, T. Akutagawa, S. Noro, S. Nishihara, T. Nakamura, Y. Yoshida, K.
Inoue, J. Phys. Chem. B 110 (2006) 7671.
[18] X.M. Ren, Y.X. Sui, G.X. Liu, J.L. Xie, J. Phys. Chem. A112 (2008) 8009.
[19] X.M. Ren, J. Ma, C.S. Lu, S.Z. Yang, Q.J. Meng, P.H. Wu, Dalton Trans. (2003)
1345.
[20] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structure,
University of Göttingen, Germany, 1997.
[21] D.C. Johnston, R.K. Kremer, M. Troyer, X. Wang, A. Klümper, S.L. Bud’ko, A.F.
Panchula, P.C. Canfield, Phys. Rev. B 61 (2000) 9558.
early up to x 6 0.5, and it is expressed as TC = 182(3)–139(13)x (K).
Compared with the [NO2BzPy][AuxNi1ꢀx(mnt)2] system, where
TC = 180(2)–221(12)x (K), the [NO2BzPy][CuxNi1ꢀx(mnt)2] system
exhibits higher x value of the transition collapsing and smaller x
dependence of TC shift.
4. Conclusion
Summarily, we synthesized and characterized structurally
five nonmagnetic doped compounds with a formula [NO2BzPy]