Magnetic properties of NiCuZn ferrites synthesized by oxalate precursor method

Article abstract of DOI:10.1016/j.jmmm.2005.11.041

Ni-Cu-Zn ferrites have been synthesized by employing co-precipitation technique using oxalate precursors. X-ray diffractograms did not show impurity phases, indicating single-phase formation of the ferrites. The diffractograms of oxalate complex decomposed at 650 °C show that ferritization is complete up to 650 °C. Lattice parameter a (A?) was found to decrease with the addition of Ni²⁺ which is attributed to ionic sizes of Ni²⁺ (0.69 A?), which replaces Cu²⁺ (0.72 A?). From the thermogravimetric studies it is observed that the experimentally observed total mass loss (%), agrees with theoretically calculated mass loss (%) indicating maintenance of requisite stoichiometry. Initial permeability (μ_i ) shows increase when Ni²⁺ is added up to x = 0.15 while for (x > 0.15), it decreases. The increase in initial permeability (μ_i) is attributed to monotonic increase in Ms, and K₁ on addition of Ni²⁺. However, the microstructure and density (porosity) also influence μ_i variations. The decrease in μ_i is attributable to increase of K_1. The composition with density 91.14% exhibits large μ_i which also tends to increase with temperature up to 60 °C. Thus its usable range extends up to 60 °C. This samples has T_c near to 160 °C.

Full text of DOI:10.1016/j.jmmm.2005.11.041

ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
www.elsevier.com/locate/jmmm
Magnetic properties of NiCuZn ferrites synthesized
by oxalate precursor method
a
a
b
a,
S.A. Ghodake , U.R. Ghodake , S.R. Sawant , S.S. Suryavanshi , P.P. Bakare
Ã
c
a
Department of Physics, Applied Electronics, Solapur University, Kegaon, Solapur 413 255, India
b
Department of Electronics, Shivaji University, Kolhapur 416 004, India
c
Centre for Material Characterization, National Chemical Laboratory, Pune 411008, India
Received 13 December 2004; received in revised form 16 November 2005
Available online 8 February 2006
Abstract
Ni–Cu–Zn ferrites have been synthesized by employing co-precipitation technique using oxalate precursors. X-ray diffractograms did
not show impurity phases, indicating single-phase formation of the ferrites. The diffractograms of oxalate complex decomposed at 650 1C
2
+
˚
show that ferritization is complete up to 650 1C. Lattice parameter a (A) was found to decrease with the addition of Ni
attributed to ionic sizes of Ni
which is
(0.72 A). From the thermogravimetric studies it is observed that the
experimentally observed total mass loss (%), agrees with theoretically calculated mass loss (%) indicating maintenance of requisite
2
+
2+
˚
(0.69 A), which replaces Cu
˚
2
+
stoichiometry. Initial permeability (m ) shows increase when Ni is added up to x ¼ 0:15 while for (x40:15), it decreases. The increase
i
2
+
in initial permeability (m ) is attributed to monotonic increase in Ms, and K on addition of Ni . However, the microstructure and
i
1
density (porosity) also influence m
i
variations. The decrease in m
i
is attributable to increase of K1. The composition with density 91.14%
exhibits large m
near to 160 1C.
r 2006 Elsevier B.V. All rights reserved.
i c
which also tends to increase with temperature up to 60 1C. Thus its usable range extends up to 60 1C. This samples has T
Keywords: XRD; Magneticproperties; Magnetization; Initial permeability; NiCuZn ferrites
1
. Introduction
precursor compound with intended stoichiometry is pre-
pared first, which is decomposed at temperatures (o873 K)
in a subsequent calcinations reaction to obtain the required
metal oxides [6]. The oxalate precursors are usually
preferred due to their low solubility, low decomposition
temperature, and very fine particle nature [7].
Polycrystalline ferrites have been extensively used in
many electronic devices, because of their high permeability
in the radio frequency (RF) region, high electrical
resistivity, mechanical hardness, and chemical stability.
There has been a growing interest in Ni–Cu–Zn ferrites for
the applications in producing multilayer type chips mainly
because these oxides can be sintered at relatively low
temperature with a range of compositions.
The quest for ceramic materials with high density, high
purity, and high permeability has led to the investigation
and evaluations of various unconventional preparative
methods. Precursors are advantageous because they ensure
excellent stoichiometry, low trace impurity content and
maximum homogeneity [1–5]. For chemical synthesis, a
Ideally, in order to achieve a complete reaction within
the shortest time and at the lowest possible temperatures,
mixing of component cations on an atomic scale is
necessary. Compound precursors achieve this goal, but
the stoichiometry of the precursors does not often strictly,
coincide with the stoichiometry of the desired product [8].
Various authors [9,10] have investigated co-precipitation of
metal oxalates from appropriately composed solutions in
order to produce precursor compounds for spinel ferrites
MFe O . Wickham [11] has synthesized spinel ferrites
2
4
2
+
2+
2+
2+
2+
MFe O (where M ¼ Mg , Ni , Zn , Mn , CO ) in
2
4
Ã
air at 873 K. Schroder [12] concluded that decomposition
of mixed oxalates is an apparently low-temperature
Corresponding author.
E-mail address: sssuryavanshi@rediffmail.com (S.S. Suryavanshi).
0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmmm.2005.11.041

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S.A. Ghodake et al. / Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
111
phenomenon. Wang et al. [13] have synthesized NiCuZn
ferrites by a ceramic method.
analyzed. The XRD patterns revealed a single spinel
structure and indicated the absence of any other impurity
Zhang et al. [14] have synthesized NiCuZn ferrites by gel
self-propagation method. They obtained ultra-fine and
highly reactive NiCuZn ferrite powder by gel self-
propagating method and concluded that densification of
ferrites and homogeneous grain growth were the main
factors affecting high initial permeability. In the present
paper, we report the synthesis of NiCuZn ferrites by
oxalate precursor method. The method is advantageous in
obtaining homogenous solid solutions of oxalates, which
on further decomposition yield the required ferrite
compositions. Chemical analysis of ferrite compositions
has been carried out by thermogravimetry. Thermal
analysis has been carried out for determination of
ferritization temperatures by simultaneous recording of
thermogravimetry (TG)/differential thermogravimetry
phase. To study m the powder obtained was compacted at
i,
2
9
1.07 ꢂ 10 dyn/cm for 1 min. into toroid form (outer
diameter ¼ 2 cm, inner diameter ¼ 1 cm). The toroids were
finally sintered at 1000 1C for 4 h. The rate of heating was
100 1C/h and the rate of cooling was 60 1C/h.
2.1.3. Saturation magnetization measurements (Ms) and
initial permeability (mi)
Saturation magnetization was measured by the vibrating
sample magnetometer (VSM) technique EG and G
Princeton Applied Research Corporation (PARC) VSM
model 4500. Initial permeability measurements of samples
were carried out using HP-4284 A precision LCR meter in
the range from room temperature to 450 1C at 1 KHz from
low field inductance measurements of coils with toroidal
cores using formula
(
DTG)/differential thermal analysis (DTA) plots (simulta-
neous thermal analysis STA) and also to confirm the
experimental results of the thermogravimetry. X-ray
diffraction (XRD) studies have been carried out to
characterize the single spinel phase. Initial permeability,
and magnetization studies have also been reported.
2
m ¼ L=ð0:0046N h log d2=d1Þ
(1)
i
where L is the inductance in mH, N the number of turns, d2
the outer diameter, d the inner diameter, h the height of
core in cm, and m the initial permeability in mH/cm.
1
2
. Experimental procedure
i
2
.1. Synthesis
The oxalates were prepared by a method suggested by
Wickham [15] and subsequently modified by Bremer et al.
[
16] for the preparation of manganese zinc ferrites.
Iron acetate was prepared by adding glacial acetic acid to
the required quantity of AR grade iron metal powder to
make a solution with a slight excess of glacial acetic acid
and heating it in a CO atmosphere instead of in a N2
2
atmosphere as employed by earlier workers [16]. Required
quantities of nickel acetate, zinc acetate, copper acetate
and the above synthesized iron acetate (total metal ion
concentration ¼ 0.45 M) were slowly added to oxalic acid
solution (0.60 M) to precipitate the required oxalate to
maintain the desired stoichiometry. In this way, different
oxalate complexes of the general composition Ni Cu
x
Zn Fe (C O ) ꢁ nH O (where t ¼ 0:45, 0.50, 0.55,
[
(1ꢀt)ꢀx]
t
2
2
4
2
0
0
.60 and x ¼ 0:00, 0.05, 0.10, 0.15, 0.20,0.30,0.40, 0.50, and
.55) were synthesized.
2
.1.1. Thermogravimetric (TG) studies
TG studies of oxalate complexes were carried out in the
temperature range of room temperature to 700 1C. The
percentage of weight loss of samples before and after
heating was calculated from the experimental data.
2
.1.2. X-ray diffractograms (XRD)
The co- precipitated oxalates were decomposed in the air
at 650 1C for 1 h. XRD patterns (Fig. 1) of this powder
material were recorded, by a Phillips X-ray Diffracto-
meter model PW-1710, using CuKp radiation and then
2 4
Fig. 1. XRD pattern for Ni0.15Cu0.30Zn0.55Fe O .

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S.A. Ghodake et al. / Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
112
3
. Results and discussion
Tables 2–4 give stepwise mass loss in percent of
experimentally observed TG curves during dehydration
and decomposition steps vis-a-vis theoretical ones. The
3
.1. Thermogravimetric (TG) studies
`
corresponding onset and termination temperature for these
steps observed from TG/DTG/DTA curves have been
given in Tables 5–7 respectively.
The temperature ranges for the different steps observed
during dehydration and decomposition processes for each
separate required metal oxalate system represented by
3.2. X-ray diffractograms (XRD)
2
+
2+
2+
2+
MFe (C O ) ꢁ nH O (M ¼ Ni , Cu , Zn , Fe ) have
2
2
4 3
2
been reported by Duval [17] and are presented in Table 1.
In case of decomposition of zinc oxalate to zinc oxide,
the required maximum temperature is 590 1C, and that for
nickel oxalate to nickel oxide, the range is 272–633 1C. In
order, to ensure the completion of dehydration and
decomposition of oxalate complexes, the calcinations
temperature was maintained at 650 1C for 1 h.
In order to confirm the single-phase formation of decompo-
sed oxalate complexes and the end ferrite, XRD studies have
been carried out. The following observations have been made:
ꢃ XRD patterns show that all samples have a single spinel
phase, indicating the absence of any other impurity
phase.
Table 1
Thermo analytical data for individual oxalates
Oxalate
Stable up to (1C)
Dehydration (1C)
Stable as anhydrous oxalate (1C)
Decomposition (1C)
NiC
CuC
2
O
4
ꢁ 2H
2
O
98
—
98–232
—
232–272
100–270
272–633—NiO
288 (Abrupt)
2
O
4
ꢁ 5H
2
O
4
94—CuO(Black)
280–590
90—ZnO
195(Two stages)
ZnC
2
O
4
ꢁ 2H
2
O
75
—
75–165
—
Unstable
—
5
2
Fe C
2
O
4
Table 2
Stepwise and total mass loss in percent and its variation with x for the oxalate complex system, Ni
x
2 2 4 3 2
Cu0.55ꢀxZn0.45 Fe (C O ) nH O
X
Proposed formulae for oxalate Stepwise and total mass loss in percent
complexes
TG experimental
TG theoretical
Dehydration
21.01
Dehydration
20.01
Decomposition
38.38
Total
58.39
Decomposition
35.60
Total
56.91
0
0
0
0
.00
Cu0.55Zn0.45
Fe
2
(C
2
O
4
)
3
ꢁ 6.5 H
2
O
.03
.10
.30
Ni0.03Cu0.52Zn0.45 Fe
2
(C
(C
(C
2
O
4
)
3
ꢁ
19.65
19.79
19.95
38.61
37.73
37.77
58.26
57.52
57.72
21.01
21.03
21.06
35.91
35.93
35.99
56.92
56.96
57.05
2
6.5H O
Ni0.1Cu0.45Zn0.45 Fe
2
2
4
O )
3
ꢁ
2
6.5H O
Ni0.03Cu0.25Zn0.45 Fe
2
O
2 4
)
3
2
6.5H O
Table 3
Stepwise and total mass losses in percent and its variation with x for the oxalate complex system, Ni
x
Cu0.5ꢀxZn0.5 Fe
2
(C
2
O
4
)
3
ꢁ nH
2
O
X
Proposed formulae for oxalate
complexes
Stepwise and total mass loss in percent
TG experimental
TG theoretical
Dehydration
Decomposition
Total
Dehydration
Decomposition
Total
0
0
0
0
.00
Cu0.5Zn0.5 Fe
2
(C
2
O
4
)
3
ꢁ 6.5 H
2
O
19.22
19.47
20.03
21.10
38.43
37.60
38.36
37.49
57.65
57.07
58.39
58.59
21.01
21.01
22.28
22.32
35.89
35.90
35.35
35.41
56.90
56.92
57.64
57.74
.03
.10
.30
Ni0.03Cu0.52Zn0.5 Fe
2
(C
2
O
4
)
3
ꢁ 6.5H
2
O
Ni0.1Cu0.4Zn0.5 Fe
Ni0.3Cu0.2Zn0.5 Fe
2
(C
(C
2
O
4
)
)
3
3
ꢁ 7H
ꢁ 7H
2
O
O
2
2
O
4
2

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S.A. Ghodake et al. / Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
113
Table 4
Stepwise and total mass losses in percent and its variation with x for the oxalate complex system Ni
x
Cu0.45ꢀxZn0.55 Fe
2
(C
O
2 4
)
3
2
ꢁ nH O
X
Proposed formulae for oxalate
complexes
Stepwise and total mass loss in percent
TG experimental
TG theoretical
Dehydration
Dehydration
Decomposition
Total
Decomposition
Total
0
0
0
0
.00
Cu0.45Zn0.55 Fe
2
(C
2
O
4
)
(C
3
ꢁ 6.5 H
2
O
19.65
21.18
20.29
20.25
37.17
37.99
37.20
35.51
56.82
59.15
57.49
55.76
21.00
22.26
21.02
19.76
35.89
35.32
35.92
36.57
56.89
57.59
56.94
56.33
.03
.10
.30
Ni0.03Cu0.42Zn0.55 Fe
2
2
O
4
)
3
ꢁ 7H
ꢁ 6.5H
ꢁ 7H
2
O
Ni0.1Cu0.45Zn0.55 Fe
Ni0.3Cu0.15Zn0.55 Fe
2
(C
(C
2
O
O
4
)
)
3
3
2
O
2
2
4
2
O
Table 5
Onset and termination temperatures (1C) observed during dehydration
Table 8
2
+
Lattice parameter variation with Ni
Ni Ni
content in ferrite systems
and Ni
and decomposition steps for Ni
system with varing x
x
Cu0.55ꢀx Zn0.45 Fe
2
(C
2
O
4
)
3
ꢁ nH
2
O
x
Cu0.55–xZn0.45Fe
2
O
4
,
x
Cu0.50–xZn0.50Fe
2
O
4
x
Cu0.45–x
2 4
Zn0.55Fe O
x
TG
X
Lattice parameter Oxalate
complex decomposed at 650 1C
Finally sintered at
1000 1C
Dehydration (step I)
Decomposition (step II)
(
0.00
a) Ni
x
Cu0.55–xZn0.45Fe
2 4
O
Onset
1C)
Termination
(1C)
Onset
(1C)
Termination
(1C)
8.408
8.407
8.417
8.416
8.411
8.410
8.409
8.405
8.404
8.403
8.393
(
0
0
0
0
0
0
0
0
.05
.10
.15
.20
.30
.40
.50
.55
8.405
8.404
0
0
0
0
.00
116
118
130
99
188
177
178
174
188
177
178
174
347
331
330
351
.03
.10
.30
8.401
8.395
8.391
8.387
8.386
Table 6
Onset and termination temperatures (1C) observed during dehydration
(
b) Ni
x
Cu0.50–xZn0.50Fe
2 4
O
0
0
0
0
0
0
0
0
.00
.05
.10
.15
.20
.30
.40
.50
8.415
8.409
8.434
8.432
8.419
8.416
8.414
8.410
8.409
8.407
and decomposition steps for Ni
with varing x
x
Cu0.5ꢀxZn0.5 Fe
2
(C
2
4
O )
3
2
ꢁ nH O system
8.409
8.406
x
TG
8.406
8.404
Dehydration (step I )
Decomposition (step II)
8.402
8.399
Onset
1C)
Termination
(1C)
Onset
(1C)
Termination
(1C)
(
(
c) Ni
x
Cu0.45–xZn0.55Fe
2 4
O
0
0
0
0
0
0
0
0
.00
.05
.10
.15
.20
.30
.40
.50
8.435
8.430
8.452
8.439
8.437
8.436
8.428
8.428
8.423
8.416
0
0
0
0
.0
116
118
112
142
204
186
180
196
204
188
180
196
326
333
353
353
.03
.10
.30
8.428
8.427
8.426
8.423
8.420
8.418
Table 7
Onset and termination temperatures (1C) observed during dehydration
and decomposition steps for Ni
with varing x
x
Cu0.45ꢀxZn0.55 Fe
2
(C
2
4
O )
3
2
ꢁ nH O system
x
TG
Dehydration (step I )
ꢃ Studies of lattice parameters on samples of end product
sintered at 1000 1C have been carried out using
experimental XRD data. From Table 8, it can be
concluded that the end ferrites exhibit a decreasing trend
in the compositional variation of the lattice parameter,
Decomposition (step II)
Onset
1C)
Termination
(1C)
Onset
(1C)
Termination
(1C)
(
2
+
˚
0
0
0
0
.00
100
103
104
131
182
182
178
185
182
182
178
185
366
353
346
345
which can be related, with ionic sizes of Ni
(0.69 A)
2
and Cu (0.72 A).
+
.03
.10
.30
˚
ꢃ Ferritization is complete at 650 1C, since the XRD
patterns (Fig. 1) at 1000 1C show similar planes. No

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S.A. Ghodake et al. / Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
114
additional prominent lines appear at 1000 1C. Thus
there no un-decomposed phases at 650 1C. The XRD
lines are not broad in both the cases, which show the
grains are not very fine.
ꢃ No structural change was observed from the XRD of
the samples sintered at 1000 1C since the samples were
slow cooled.
3
.3. Compositional variation of initial permeability (mi)
Initial permeability was determined by winding 100 turns
of 30 SWG enameled copper wire on toroids, and
inductance is measured at various frequencies ranging
from 20 Hz to 700 kHz using Hewlett packard LCR-Q
meter 4284A.The m was calculated using relation (1).
i
The m measurements for compositional variation studies
i
were carried out at room temperature, and in case of
thermal variation studies from room temperature to 450 1C
at 1 KHz.
2
+
From Fig. 2, it is observed that with increase in Ni
content m increases initially and then decreases. In Tables
i
9
–12 data on initial permeability (m ), rotational perme-
i
ability (m ), wall permeability (m ) are given at room
rk
w
temperature. The values of rotational permeability have
been calculated using formula
Fig. 2. Compositional variation of initial permeability (m
Ni Cu Zn Fe O .
i
)
for
2
s
mrk ¼ 1 þ 2PM =jK j
(2)
(3)
1
x
(1ꢀt)ꢀx)
t
2
4
The wall permeability
Table 9
Data on initial permeability (m
permeability (m ) with Ni
m ¼ m ꢀ ðm ꢀ 1Þ
w
i
rk
i
), rotational permeability (mrot), and wall
w
x
Cu[(1ꢀt)ꢀx]Zn Fe
t 2
O
4
with t ¼ 0:45
where M is the saturation magnetization, K is anisotropy
1
constant, from Tables 9–12 it is clearly seen that the
magnitude of wall permeability m is large in comparison
s
4
X
m
i
m
rot
m
w
ꢀK
1
ꢂ 10 (erg/ Density
3
cm )
(%)
w
with rotational permeability mrk in all compositions of
0
.00
497
635
585
603
487
279
371
300
129
21
20
22
22
23
26
26
27
25
477
616
564
582
465
254
346
274
105
3.30
3.34
3.37
3.40
3.44
3.51
3.58
3.65
3.69
91.50
89.56
90.28
94.28
96.02
95.13
96.21
99.40
97.79
Ni Cu
Zn Fe O . Thus it is concluded that the main
0.05
0.10
x
[(1ꢀt)ꢀx]
t
2
4
contribution to the initial permeability is due to domain
wall motion. Hence Globus model is applicable [18] for the
present studies.
0
0
0
0
0
0
.15
.20
.30
.40
.50
.55
2
s
m ¼ M D=K
(4)
i
1
where D is the grain size. Initial permeability (m ) shows
i
2
+
increasing trend on addition of Ni ions up to x ¼ 0:15,
Table 10
Data on initial permeability (m
permeability (m ) with Ni
while for x40:15, it exhibits decreasing trend. The
i
), rotational permeability (mrot), and wall
contribution to m comes from magneto-crystalline aniso-
w
x
Cu[(1ꢀt)ꢀx]Zn Fe
t 2
O
4
with t ¼ 0:50
i
tropy constant (K ), saturation magnetization (M ) and
grain size (D). K and M values increase with addition of
4
1
s
X
m
i
m
rot
m
w
ꢀK
1
ꢂ 10 (erg/ Density
3
cm )
1
s
(%)
2
Ni . It can be concluded that effect of M appears to be
+
s
0
0
0
.00
627
790
1058
1086
782
717
905
273
18
21
18
25
26
26
29
28
610
770
3.00
3.04
89.80
90.38
87.73
94.27
86.44
92.25
98.02
97.32
dominant to increase m up to x ¼ 0:15, while for x40:15
i
.05
.10
the effect of K appears to dominate reducing m . Density
1
i
1041 3.07
1062 3.11
has no effect on the trend exhibited by mi.
0.15
0
0
0
0
.20
.30
.40
.50
757
692
877
246
3.14
3.21
3.28
3.35
3
.3.1. Thermal variation of initial permeability (mi)
Figs. 3–5 show thermal variation of initial permeability
0
00
m . Its real part m and imaginary part m vary with
i

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115
Table 11
temperature of each composition in the range from room
temperature to the Curie temperature T . Near T both m ,
i
Data on initial permeability (m ), rotational permeability (mrot), and wall
permeability (m
c
c
i
w
) with Ni
x
Cu[(1ꢀt)ꢀx]Zn
t
Fe
2
O
4
with t ¼ 0:55
0
0
and m drop to zero sharply. A sharp decrease in m and m at
i
4
3
T suggests single-phase formation of the ferrite material.
x
m
i
m
rot
m
w
ꢀK
1
ꢂ 10 (erg/cm )
Density (%)
c
This observation supports the conclusion drawn from
the XRD analysis that all the compositions are single
phase.
0
0
0
0
0
0
0
0
.00
1089
1068
1544
2401
1854
1700
797
36
16
19
23
22
25
26
6
1054
1853
1526
2379
1833
1676
772
2.70
2.70
2.77
2.81
2.84
2.91
2.98
3.02
89.52
86.01
86.72
91.14
88.60
96.24
99.13
95.80
.05
.10
.15
.20
.30
.40
.50
In most of the magnetic materials, m increase with
i
temperature up to T . This is because the anisotropy field
usually decreases faster with temperature than M [18].
c
s
Both Enz [19] and Ohta [20] have shown that the initial
permeability m is maximum at the temperature where the
455
450
i
anisotropy constant K changes sign. In our present studies
1
we have observed peaking behavior in the m –T variation.
i
The peak observed is due to the rapid change in K with
respect to the temperature than the magnetization M . At
1
s
Table 12
Data on initial permeability (m
permeability (m ) with Ni
T the material becomes nonmagnetic making m ¼ 0 at
i
), rotational permeability (mrot), and wall
c
i
that temperature.
From the thermal variation of m , it is seen that with the
w
x
Cu[(1ꢀt)ꢀx]Zn
t
Fe
2
O
4
with t ¼ 0:60
0
0
4
3
X
m
i
m
rot
m
w
ꢀK
1
ꢂ 10 (erg/cm )
Density (%)
00
increase of temperature m increases, reaches a maximum
near T and then falls sharply near to T . The loss becomes
large near to T , which may be due to the damping effect
0
0
0
0
0
.05
1224
1267
1729
1691
599
13
16
18
20
25
1212
1252
1712
1672
575
2.44
2.47
2.51
2.54
2.61
98.39
98.47
99.03
99.04
99.07
c
c
.10
.15
.20
.30
c
on the domain walls.
The loss factor (LF) is defined by LF ¼ tan d=m . For
i
a good ferrite LF should be as low as possible. In
0
Fig. 3. Thermal variation of initial permeability (m
Ni
i
)
for
Fig. 4. Thermal variation of initial permeability (m
(0.45ꢀx)Zn0.55Fe O .
2 4
i
)
for Ni
x
Cu
x
Cu(0.45ꢀx)Zn0.55Fe
O
2 4
.

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116
0
0
Fig. 5. Thermal variation of initial permeability (m ) for
i
x 2 4
Ni Cu(0.45ꢀx)Zn0.55Fe O .
x 2 4
Fig. 6. Thermal Variation of loss factor for Ni Cu(0.45ꢀx)Zn0.55Fe O .
Fig. 6 thermal variation of LF for the compositions
Ni Cu Zn0.55Fe O are shown. In the temperature
x
(0.45ꢀx)
2
4
range 25 1C to near T , it is found that LF is almost
The loss factor is found to decrease initially with increase
in frequency for all the compositions. Minimum values are
attained in the range 100–10 KHz; as shown in Fig. 9,
followed by an increase.
c
constant, while above T the loss factor increases exponen-
tially. The thermal variation of m seems to be responsible
c
i
for increase in loss factor. In order to have low loss factor
the ferrite must be operated at low temperature.
3.4. Saturation magnetization (Ms)
3
.3.2. Frequency dependence
0
00
In Figs. 7, 8 variation of m and m with frequency in the
range 20 Hz to 1 MHz, for the composition Nix-
Cu( Zn0.55 Fe O , are shown. Rado [21] and others
From Table 13 it is seen that 4P M and (n ) increase
s
B
2
with addition of Ni ions. The increase in magnetization
+
2
with addition of Ni ions can be explained on the basis of
+
0.45ꢀx)
2
4
2
+
2+
[
22–25] observed high-frequency dispersion and absorption
magnetic moment of Cu
2
When x amount of Ni
(1.3 m ) and Ni
(2.3 mB).
ions are
B
+
2+
in m and attributed it to rotational resonance in the
ions are added Cu
i
combined anisotropy and demagnetizing fields while the
low frequency dispersion was attributed to the domain wall
decreased by amount [(1ꢀt)ꢀx]. The magnetic moment of
2+ 2+
Ni is greater than that of Cu and both the ions occupy
0
2+
B-site. Hence the addition of Ni leads to an increase in
displacement. From Figs. 7 and 8 frequency variation of m
0
0
and m clearly indicate the low-frequency dispersion which
may be attributed to the domain wall movement. We have
magnetic moment of B-sub lattice. As a result, the
+
magnetization goes on increasing with addition of Ni
2
already shown that the major contribution to m is due to
Ms in addition depends on the porosity, which has
demagnetizing effect. The density values of the samples
are variable and this factor also contributes towards the
i
domain wall movement. We have already shown that the
major contribution to m is due to domain wall displace-
i
ment, which is manifested here by the low-frequency
dispersion. The dispersion at high frequencies ( ¼ 1 MHz)
is attributed to spin resonance in the internal anisotropy
field.
trend in M exhibited in the present studies. The magnetic
s
properties of the samples (with low density) show
unsatisfactory magnetic properties. The highest value
of the density achieved is 99.40 for the composition

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117
0
Fig. 7. Frequency variation of initial permeability (m
i
x 2 4
) for Ni Cu(0.45ꢀx)Zn0.55Fe O .
0
0
Fig. 8. Frequency variation of initial permeability (m ) for Ni
x 2 4
Cu(0.45ꢀx)Zn0.55Fe O .
i
Ni0.5Cu0.05Zn0.45Fe O that exhibits highest value of
4
Table 14 summarizes properties of Ni0.38Cu0.12Zn0.5Fe O
2 4
2
saturation magnetization.
Wang et al. [13] have synthesized NiCuZn ferrites by the
ceramic method, which places a restriction on the higher
synthesized by Wang et al. [13]; Ni0.15Cu0.25Zn0.5Fe1.96O4
synthesized by Zhang et al. [14] and by us Ni0.40Cu0.10Zn0.5
Fe O (a), Ni0.15Cu0.25Zn0.60Fe O . It is clearly seen that
although the sintering temperature and time are compar-
able, our ferrite shows superior/improved magnetic proper-
ties. The initial permeability values of our ferrite is about
twofold greater than the values reported [13,26], also
density is greater than reported by [13,26].
2
4
2
4
2
+
temperature sintering due to Cu ions and restriction on
densification. This may tend to lower 4PM values of these
s
ferrites when synthesized by ceramic method. However,
chemical method overcomes this problem, and due to
fine particle size, densification 4PM value may improve.
s

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118
Fig. 9. Frequency variation of loss factor (LF) for Ni
x 2 4
Cu(0.45ꢀx)Zn0.55Fe O .
Table 13
References
s B
Compositional variation of 4PM , n , and porosity for the ferrite system
Ni
x
Cu [(1ꢀt)–x]Zn
t
Fe
2
O
4
at 300 K and 77 K with t ¼ 0:45 and 0.55
[
[
[
1] M.N. Sankarshana Murthy, C.E. Deshpande, P.P. Bakare,
J.J. Shrotri, Bull. Chem. Soc. Jpn. 52 (2) (1979) 571.
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Ind. J. Chem. 26A (1987) 1.
X
4PMs
00 K G
n
B
4PMs
77 K G
n
B
Porosity
3
300 K
77 K
3] K.C. Patil, S. Sundar Manoharam, D. Gajpathy, in: N.P. Cher-
emisinoff (Ed.), Handbook of Ceramics and Composites, Part I,
Marcel Dekker, NewYork, 1990, p. 469.
(a) t ¼ 0:45
0
0
0
0
0
0
0
.00
.05
.10
.15
.20
.30
.40
4074
2.61
2.55
2.68
2.68
2.81
3.01
3.04
7077
7086
7173
7195
7365
7629
7643
4.53
4.53
4.58
4.59
4.70
4.86
4.86
9
10
10
6
3997
4205
4209
4421
4722
4781
[
[
4] P.P. Bakare, V.G. Ganjikar, C.E. Deshpande, S.K. Date, J. Mater.
Sci. 26 (1991) 484.
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A.B. Mandale, S.K. Date, Bull. Mater. Sci. 17 (6) (1994)
4
5
1
015.
4
[
6] M. Bremer, S. Fisher, H. Topelmann, H. Scheler, Thermochim. Acta
209 (1992) 323.
(b) t ¼ 0:55
0
0
0
0
0
0
0
0
.00
.05
.10
.15
.20
.30
.40
.45
4855
3207
3549
3948
3906
4202
4322
1999
3.14
2.07
2.29
2.54
2.51
2.70
2.77
1.28
6526
6801
7079
7374
7387
7739
7830
3597
4.23
4.38
4.56
4.75
4.74
4.97
5.02
2.30
10
14
13
9
[7] M. Paulus, in: O. Hagenmuller (Ed.), Preparative Methods
in Solid State Chemistry, Academic Press, New York, 1972,
p. 487.
[
8] J.M. Longo, H.S. Horowitz, L.R. Clevenna, in: S.L. Holt,
J.L. Milstein, M. Robbins (Eds.), Solid State Chemistry—A
Contemporary Overview, Advances in Chemistry Series, 1986,
p. 139.
11
4
1
4
[
9] W.J. Schuele, J. Phys. Chem. 63 (1959) 83–86.
[
[
10] P. Klienert, A. Funke, Z. Chem. 1 (5) (1961) 155–157.
11] D.G. Wickham Jr., in: S. Young Tyree Jr. (Ed.), Inorganic Synthesis,
vol. IX, McGraw-Hill, New York, 1967, p. 152.
Table 14
Summary of properties of Ni0.38 Cu0.12Zn0.5Fe
al. [13]; Ni0.15Cu0.25Zn0.5Fe1.96 synthesized by Zhang et al. [14] and by
(a), Ni0.15Cu0.25Zn0.60Fe
2
4
O synthesized by Wang et
[
[
12] V.H. Schroder, Z. Phys. Chem. 236 (1967) 200–212.
13] S.F. Wang, Y.R. Wang, C.K. Wang, C.F. Chen, C.A. Lu,
C.Y. Huang, J. Magnetism Magn. Mater. 220 (2000) 129–135.
14] H. Zhang, Z. Ma, J. Zhou, Z. Yue, Z. Yue, Z. Gui, J. Magnetism
Magn. Mater. 213 (2000) 304–308.
O
4
us Ni0.40Cu0.10Zn0.5Fe
2
O
4
2 4
O
[
[
[
[
[
Method
Wang et al. Zhang et al.
13] solid-state [14] Gel self-
propagating
Co-precipitate
oxalate
precursor
[
reaction
15] D.G. Wickham, Inorganic Synthesis, vol. IX, McGraw-Hill, New
York, 1967, p. 152.
16] M. Bremer, St. Fischer, H. Langbein, W. Topelmann, H. Scheler,
Thermochim. Acta. 209 (1992) 323–330.
Sintering temperature 1250 1C
and time
900 1C
1000 1C
17] C. Duval, Inorganic Thermogravimetric Analysis, second ed., Else-
vier, Amsterdam, 1963 223,330,387,411.
2 h
4.94 g/cm
4 h
4.76 g/cm
4 h
5.215(a)
2
2
Density
18] A. Globus, P. Duplex, Phys. Stat. Solidi 31 (1969) 875.
5
.239(b)
905 (a)
729 (b)
Initial permeability
387
900
[19] U. Enz, Proc. Inst. Elect. Eng. 109 B (1961) 246.
[20] K. Ohta, J. Phys. Soc. Japan, 18 (1963) 685.
1
[21] G.T. Rado, Rev. Mod. Phys. 25 (1953) 81.

ARTICLE IN PRESS
S.A. Ghodake et al. / Journal of Magnetism and Magnetic Materials 305 (2006) 110–119
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22] G.T. Rado, V.J. Floen, W.H. Emerson, Proc. Instn. Elect. Engrs. B
045 (1957) 198.
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[25] A.M. Sankpal, S.V. Kakatkar, N.D. Choudhari, R.S. Patil,
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173–179.
1
[
[
24] G.T. Rado, R.W. Wright, W.H. Emerson, Phys. Rev. 80 (1950)
[26] H. Zhang, Z. Ma, J. Zhou, Z. Yue, L. Li, Z. Gui, J. Magn. Magn.
Mater 213 (2000) 304.
273.