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Journal of Magnetism and Magnetic Materials 322 (2010) 3064–3071

Contents lists available at ScienceDirect

Journal of Magnetism and Magnetic Materials

0304-88

doi:10.1

n Corr

E-m

journal homepage: www.elsevier.com/locate/jmmm

The role of copper ions on the structural and magnetic characteristicsof MgZn ferrite nanoparticles and thin films

Ali Ghasemi a,n, Azadeh Ashrafizadeh a, Andrea Paesano Jr.b, Carla Fabiana Cerqueira Machado b,Sagar E. Shirsath c, Xiaoxi Liu a, Akimitsu Morisako a

a Spin Device Technology Center, Faculty of Engineering, Shinshu University, Japanb Centro de Ciencias Exatas, Departmento de Fisica, Universidade Estadualde de Maringa, Parana, Brazilc Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, India

a r t i c l e i n f o

Article history:

Received 1 March 2010

Received in revised form

15 May 2010Available online 24 May 2010

Keywords:

Ferrite

Magnetic property

Nanoparticle

Thin film

53/$ - see front matter & 2010 Elsevier B.V. A

016/j.jmmm.2010.05.031

esponding author.

ail address: ali13912001@yahoo.com (A. Gha

a b s t r a c t

In this study CuxMg0.5�xZn0.5Fe2O4 (x¼0–0.5) nanoparticles and thin films were prepared by sol–gel

processing. The morphologies of nanoparticles were observed by transmission electron microscope

(TEM). The Mossbauer spectroscopy (MS) was employed to determine the site preference of the

constitutive elements. Magnetic dynamics of the nanoparticles was studied by the measurement of

AC magnetic susceptibility versus temperature at different frequencies. The phenomenological

Neel–Brown and Vogel–Fulcher models were employed to distinguish between interacting or

non-interacting system. Results exhibited that there is strong interaction between fine particles.

X-ray diffraction (XRD) patterns of the thin films indicate the formation of single-phase cubic spinel

structure. Atomic force microscope (AFM) was employed to evaluate the surface morphologies of the

prepared thin films. Vibrating sample magnetometer (VSM) was employed to probe magnetic

properties of samples. It was found that with an increase in the amount of copper, the saturation of

magnetization and initial permeability increase.

& 2010 Elsevier B.V. All rights reserved.

1. Introduction

Soft magnetic materials have great potential application inelectronic industry. The most common type is cubic spinel ferriteswith formula AB2O4, which contains tetrahedral (A site) andoctahedral (B site) crystalline sites. The magnetic and electricalproperties of soft ferrite could be easily tuned by incorporationand suitable distribution of additional cations (divalent ortrivalent) in the spinel structure. Nanocrystalline ferrite thinfilms have potential applications in high-density magneto-opticrecording devices, color imaging, bioprocessing, ferrofluids,magnetic refrigeration and monolithic microwave integratedcircuits (MMICs) [1–7].

MgZn ferrite in thin film configuration and powder forms hascubic spinel structure and is widely used in many electronicdevices because of high electrical resistivity, hard mechanicalproperties, high Curie temperature and environmental stability.Several investigators have studied the magnetic and electricalproperties of MgZn ferrites in powder and bulk forms by partiallysubstituting Mg with Cu ions [8–14].

ll rights reserved.

semi).

In the recent years, we have focused our studies on thepreparation and magnetic characteristics of ferrite nanoparticles[15–19]. We felt that there are still some lags in magneticcharacteristics of this type of ferrite, particularly magneticsusceptibility of MgCuZn ferrite is not widely studied. With thisview in mind the present paper premise deals with the fabricationof MgCuZn ferrite in nanoparticles and thin films configuration bya sol–gel method. The site preference and magnetic susceptibilitycharacteristics of nanoparticles were investigated. The nanopar-ticles were dispersed in the ferrite solution (sol) in order tofabricate thin films. Magnetic properties and structural features ofthe prepared films were characterized by X-ray diffractometer,atomic force microscopy and vibrating sample magnetometer.

2. Materials and methods

2.1. Preparation of nanoparticles and thin films

The MgCuZn ferrite nanoparticles were prepared by a sol–gelmethod. The aqueous sol was produced by dissolving iron nitrate,copper nitrate, magnesium nitrate and zinc nitrate, according todesired stoichiometric proportion, in deionized water and thenmixed together by constant stirring. Citric acid was added to thesol for the enhancement of nitrates dissolution. The pH value of

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1000

900

800

700

600

500

400

300

200

100

Oka

FeLI

FeLa

CuL

IC

uLa

ZnLI

ZnLa

MgK

a

ZnLs

um

FeK

a

FeK

b

CuK

a

ZnK

aC

uKb

ZnK

b

Cou

nts

X 0.39 nm

=

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–3071 3065

solution was adjusted to 7 using ammonia. All the solutions weredark brown indicating the presence of Fe3 + ions. The gels wereobtained by slow evaporation at 70 1C until the gel dried. Then,dried gels were sintered at 800 1C for 1 h. The synthesized ferriteswith average particle size of 10 nm were dispersed in thesubsequent solution in order to fabricate thin films with dipcoating. The wet films were deposited by a dip coating method onthe substrate of Si/SiO2 and the wet films were dried at 100 1C for10 min to remove the mixed solvents. Finally, the dried films wereannealed at 800 1C for 30 min in air and cooled slowly in thefurnace. The thickness of the nanocrystalline ferrite thin films wasin the range 600–650 nm. The thickness of the films wasmeasured by the Surface Profiler, Talystep (Taylor-Hobson, UK).

2.2. Characterization of ferrite nanoparticles

The morphology and size distribution of nanoparticles wereinvestigated by transmission electron microscopy (TEM) modelJEOL 2010. Energy-dispersive X-ray spectroscopy microanalysis(EDAX) was used to probe the constitutive elements into thesamples. The MS characterizations were performed in thetransmission geometry, using a conventional spectrometer,operated in the constant acceleration mode. The g-rays wereprovided by a 57Co(Rh) source, with a nominal starting activity of25 mCi. The Mossbauer spectra were analyzed using a non-linearleast-square routine, with Lorentzian line shapes. Eventually, ahyperfine magnetic field distribution, Bhf Dist., was used ashistograms in the spectral analysis. All isomer shift (d) data aregiven relative to a-Fe throughout this paper. The AC magneticsusceptibility of nanoparticles has been measured versustemperature at different frequencies in the selected range of40–1000 Hz and 130–220 K, respectively, using a Lake Shore ACsusceptometer model 7000.

2.3. Characterization of ferrite thin films

The phase identification of thin films was performed by X-raydiffraction (XRD) using CuKa radiation. Atomic force microscopywas employed to evaluate the surface morphology of thin films.Room temperature magnetization and hysteresis loops of thefilms were measured using a VSM.

00.00 1.00 2.00 3.00 4.00 5.00

keV6.00 7.00 8.00 9.00 10.00

Fig. 1. (a) TEM micrograph and (b) EDAX result of sample x¼0.3.

3. Results and discussion

3.1. Structural properties of nanoparticles

The particle size distribution was estimated based on analyz-ing the bright field images of randomly selected nanoparticles.Table 1 reflects the range of particle size of prepared samples. Itreveals from Fig. 1(a) that the particle size of Cu0.3Mg0.2Zn0.5Fe2O4

is in the range of 7–14 nm. The value of mean particle size is inclose agreement with the XRD results. The EDAX microanalyzer ofthe mentioned sample proved the existence of the constitutiveelements. The heating thermograms of samples (not shown here)exhibited that nearly 35% of sample evaporated while heating to500 1C. The heating analysis of ferrite nanoparticles exhibit oneexothermic peak at temperature of 210 1C. The mentioned peak isattributed to the amorphous-to-crystalline phase transition.

Table 1The particles size range according to the TEM observation.

x 0 0.1 0.2 0.3 0.4 0.5

Particle size range (nm) 2–5 4–9 7–11 9–14 13–25 20–35

Fig. 2 shows the room temperature (RT) Mossbauer results forsome representative samples. The spectra revealed ferrites notcompletely magnetically ordered and were fitted consideringhyperfine magnetic field distributions (see insets, in the figures).Table 2 presents the obtained hyperfine parameters, for the wholeseries of the samples. According to this data, all the iron cationsare in the ferric state (Fe3 +). Substitution of magnesium by copperfrom X¼0.5 down to X¼0.2 does not significantly change theaverage magnetic hyperfine field. However, a clear decreaseoccurs from X¼0.1, including the appearing of a paramagneticfraction for the X¼0 sample. Since the size of nanoparticlesof sample x¼0 is in the range of 2–5 nm, the influence ofsuperparamagnetic on doublet is obvious. The doublet arises fromboth A- and B-site ferric ions. The doublet is graduallydisappeared by lowering the temperature [20]. The doubletcould also be attributed to the presence of a small amountof a secondary phase, paramagnetic at RT. Earlier results on the

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Fig. 2. Mossbauer spectra of CuxMg0.5�xZn0.5Fe2O4 with x¼0, 0.2 and 0.4.

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–30713066

copper (CuFe2O4), magnesium (MgFe2O4) and zinc (ZnFe2O4)stoichiometric ferrites have shown that only zinc ferrite is notmagnetic at room temperature [21–23]. Besides, the former is an

inverse spinel (Bhf �480 kOe/site A–512 kOe/site B), the middleone is a partially inverse spinel (degree of inversion �0.9; Bhf

�482 kOe/site A–500 kOe/site B) whereas the later is a normal

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Table 2Hyperfine parameters for the ferrite samples (IS¼ isomer shift; QS¼quadrupole

splitting; Bhf¼hyperfine magnetic field; G¼ linewidth).

Sample/Site IS (mm/s) QS (mm/s) Bhf (T) G (mm/s) Area (%)

X¼0.5 Bhf Dist. 0.31 �0.03 31.0 0.36 100

X¼0.4 Bhf Dist. 0.30 �0.03 30.7 0.35 100

X¼0.3 Bhf Dist. 0.30 �0.02 31.9 0.34 100

X¼0.2 Bhf Dist. 0.30 �0.03 31.6 0.36 100

X¼0.1 Bhf Dist. 0.29 �0.02 28.9 0.32 100

X¼0 Bhf Dist. 0.30 �0.03 26.3 0.30 85.8

Doublet 0.33 0.46 � 0.49 16.2

Table 3Magnetic parameters of nanosize and micron size particles.

x Hc (Oe)

nanosize

Hc (Oe)

micron size

Ms (emu/gm)

nanosize

Ms (emu/gm)

micron size

0 o1 9 23 73

0.1 o1 7 27 75

0.2 o1 5 29 80

0.3 o1 4 33 84

0.4 o1 4 35 87

0.5 o1 3 38 89

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–3071 3067

spinel. Therefore, it is plausible to suppose that for X¼0 thetrivalent iron is shared nearly half-and-half among the sites A andB, although this is not clearly evidenced in the respective RTspectrum. Then, decrease in the copper content implies in a‘‘migration’’ of iron cations to the octahedral (B) sites, since part ofthe magnesium cations go to the tetrahedral (A) sites. The dilutionof iron cations in site A weakens both the antiferromagnetic A–Aand A–B interactions, leading to a magnetic relaxation. As aconsequence, there is a progressive weakening of the hyperfinemagnetic field and the appearing of a paramagnetic component(i.e., the doublet) for X¼0. According to literature, in situationslike that site B is usually the first to relax and thus, more probably,the doublet belongs to the iron located at site B. Nevertheless,variations in the local iron concentration as well as the presencethroughout the sample of very small (superparamagnetic)nanocrystallites may account both the sites for the doublet.

3.2. Comparison between nanosized and bulk ferrite

It is worthy to compare the magnetic properties, particularlycoercivity and saturation of magnetization values for the preparednanosized particles with the bulk one. Interestingly, it has beenfound that the coercivity and remanence are almost zero for allnanosized samples. The samples were not saturated even atmagnetic field of 24 kOe, which reflects the characteristic ofsuperparamagnetism. The value of saturation magnetizationobtained by fitting the high field data to the functionM¼Ms(1�a/H), where M and Ms are magnetization and satura-tion magnetization, respectively, a is the fitting parameter and H

is the applied field, are given in Table 3. The variation ofmagnetization of MgCuZn ferrite nanoparticles, up to a specificmagnetic field, the magnetic moments of core align with theapplied field. Beyond that field, any increase in the magnetic fieldhas an effect on the shell of the particles and therefore the slope inthe increase of magnetization slows down. The lower values ofsaturation magnetization of nanocrystalline ferrite compared tothe micron size samples is attributed to the surface effects, whichleads to the non-collinearity of the magnetic moments on theirsurface and can be explained in terms of core–shell model ofnanoparticles in which the core contains ferrimagnetically alignedspin and the surface or interface with the certain degree of spincanting. The disordering in the shell is caused due to localchemical disorder, broken exchange bonds and different localsymmetry for those atoms near the surface [24]. Some researchersreport that, this partially disordered layer gives rise to a spincanting due to the imbalance of ferromagnetic sub-lattice [25,26].However other authors claimed that the spin canting involve thewhole particle and is not restricted to the surface layer [27]. Thevacancies or modified cation distribution weakens the super-exchange paths and therefore caused the spin canting in the coreof ferrite nanoparticles. It must be noted that if the surfactantmolecules absorb on the surface of nanoparticles and the

electrons can no longer participate in the super-exchangeinteraction, then the pinning of spin occurs [28].

3.3. Interacting or non-interacting nanoparticles?

Slow dynamics in nanoparticle systems can be classified intotwo kinds. The first one is due to the broad distribution ofrelaxation times originating solely from the anisotropy energybarriers. In this non-interacting case the magnetic moment ofeach particle relaxes according to its individual energy barrierthat depends on the magnetic anisotropy, which in turn dependson the volume of the nanoparticle. Therefore, a distribution ofparticle volumes results in a distribution of energy barriers andblocking temperatures. In the second kind of slow dynamics indense magnetic nanoparticle systems, cooperative spin-glass-likedynamics, accompanied by frustration caused by the strongdipolar interactions among the particles.

To study the magnetic dynamic behavior of the nanoparticles,we measured the AC magnetic susceptibility of prepared ferritesversus temperature at different frequencies. Fig. 3 reflects thetemperature dependence of imaginary parts w00 (T) of AC magneticsusceptibility for x¼0 at different frequencies in the range of111–1000 Hz and at an AC magnetic field of 800 A/m. In Fig. 3, w00(T) shows a peak near 200 K, which is frequency dependent andshifted to higher temperature with increase in frequency. Thischaracteristic maximum is the signature of blocking/freezingprocess of the superparamagnetic/spin glass systems [29–33]. Theblocking temperature (TB) is the threshold point of thermalactivation. Above TB, magnetocrystalline anisotropy is overcomeby thermal activation and the magnetization direction of eachnanoparticle simply follows the applied field direction.Consequently, the nanoparticles show paramagnetic properties.Below the blocking temperature, thermal activation is no longerable to overcome the magnetocrystalline anisotropy of thenanoparticles. As a consequence, the magnetization direction ofeach nanoparticle rotates from the field direction back to its owneasy axis without any movement of the nanoparticle. Since thenanoparticles and consequently their easy axes are randomlyorientated, overall susceptibility is reduced with decrease intemperature as shown in Fig. 3.

According to the Neel–Brown model, the blocking temperaturemeasured at a given working frequency, is related to theconsidered frequency as: ln 1/2pn¼ ln t0+KV/kBTB. TB can beobtained by assuming that at the maximum of the out-of phasecomponent of the susceptibility, the relaxation time matches theworking frequency. Attempt time is calculated from the curvesand it is found that it spreads between t0¼10�23 and 10�21 s.These values, however, are unphysical, being several orders ofmagnitude lower than the typical value found in the literature fora non-interacting assembly of superparamagnetic nanoparticles(10�8–10�11 s). This suggests that the Neel–Brown model is notappropriate to describe the dynamic behavior of our system.In this case, deviations from the model can be ascribed to the

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Fig. 3. Thermal variation of imaginary parts of effective magnetic susceptibility.

Fig. 4. XRD patterns of CuxMg0.5�xZn0.5Fe2O4 prepared by sol–gel processing.

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–30713068

presence on strong interactions, as indeed suggested by TEMimages that showed the presence of several large aggregates.

The interaction between nanoparticles affected the blocking/freezing temperature by modifying the potential barrier. Byincreasing the strength of interaction, TB shifts to highertemperatures. For interacting magnetic nanoparticles, the fre-quency dependence of TB is given by the Vogel–Fulcher law [29]

ln1=2pn¼ lnt0þEa=kBðT�T0Þ ð1Þ

Here Ea is the energy of barrier, T0 is an effective temperature,which reveals the existence of the interaction between nanopar-ticles and T is the characteristic temperature indicating the onsetof the blocking process. We tried to fit the experimental data ofw00(T) for our samples, using Eq. (1). It was found that the values ofattempt time are spread between 3.8�10�9 and 4.2�10�11. Inthe inset, we see that the blocking temperature increases almostlinearly with the increase in Cu concentration in the samples. Themain reason is attributed to the size of nanoparticles. Basically,with reducing Mg content and hence increasing Cu content in thecomposition the size and distributions of particles are increased.It is well known that blocking temperature has linear proportionalto the volume of particles and anisotropy constant. Consequently,it is reasonable to have the mentioned trend in blockingtemperature versus copper content. Another contributor whichmust also be considered is the amount of paramagnetic phases inthe prepared samples. It was clarified by MS results that theamount of paramagnetic phase is increased by reducing coppercontent. Therefore the anisotropy constant is higher for copperrich samples compared with the Mg rich ferrites.

3.4. Structural characteristics of ferrite thin films

The XRD patterns of samples in Fig. 4 revealed that in allsamples (except x¼0.5), by substituting Mg with Cu, no extrapeak corresponding to any secondary phases were identified. Itmust be noted that for sample x¼0, the peaks (2 2 0), (3 1 1) and(5 1 1) display an inflexion, which could be related to the presencesmall amount of secondary phase. Copper cation promotes the

solid reaction and reduces the sintering temperature. The effect ofincreasing copper content in the sample is found to be similar tothat of increase in the sintering temperature. Based on the XRDresults, it seems that copper cations could be re-arranged in thespinel structure of MgZn ferrite. It is reasonable to conclude fromthe patterns that the spinel phases can be formed in the all thespecimens at relatively low temperature.

Fig. 5 demonstrates the surface morphologies of the preparedthin films. A densely packed microstructure obtained at annealing

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x= 0 x=0.1

x=0.2 x=0.3

x=0.4 x=0.5

500×500 [nm]

500×500 [nm] 500×500 [nm]

500×500 [nm] 500×500 [nm]

500×500 [nm]

Fig. 5. Three dimensional AFM micrographs of MgCuZn ferrite on Si/SiO2 substrate.

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–3071 3069

temperatures represents the high uniformity of these films. Allthe films generally have good microstructure with few defectssuch as pinholes or microcracks. Based on the AFM micrographs, itseems that at low concentration of copper content, the solidreaction and densification process during sintering are restrainedand the porosities are formed in the grain boundaries. With anincrease in copper content, the microstructure becomes moreuniform and compact, intergranular pores disappear and grainsgrow bigger. Such a microstructure is very beneficial to the softmagnetic properties of ferrites.

The average grain size estimated from the three-dimensionalAFM images of these films was observed to increase from about20 nm (for the film with no copper addition) to 55 nm (for thefilm with the highest amount of copper).

3.5. Magnetic characteristics of ferrite thin films

Fig. 6(a) reveals narrow hysteresis curves for the preparedsamples. The synthesized MgCuZn ferrite showed a narrowhysteresis loops with high saturation magnetization and lowcoercivity. It is revealed that with increase in the amount ofcopper in the composition, saturation magnetization is increased,while coercive force is decreased. Variations of Ms with chemicalcomposition (Fig. 6b) can be explained on the basis of theexchange interaction between the ions at the tetrahedral (A) andoctahedral (B) sites. In MgCuZn ferrite, the Zn2 + ions occupy onlyat A site and Mg2 +, Cu2 + and Fe3 + ions have preference for the Bsite [34]. Even though Cu2 + has a preference for the octahedral

site, it is also shown to occupy the tetrahedral sites, when Cusubstitutes for Mg, a part of Cu2 + will occupy the tetrahedral sitesdisplacing Fe3 + ions from there to the octahedral sites. Thisincrease in the Fe3 + concentration in the octahedral sites (whichhave a magnetic moment of +5 mB) and also substituting Mg2 +

(0 mB) with Cu2 + (+1 mB) on B sub-lattice, result in an increase inmagnetic moment on the B sub-lattice, as well as the netmagnetic moment of the spinel ferrite increases. On the otherhand, besides the intrinsic factor such as the site occupancy ofcations, the saturation magnetization can be tuned by extrinsicvariables like microstructure. It is well known that withincreasing grain size, Ms can be increased. Fig. 5 clarifies thatthe grain size increases on adding copper content andconsequently the saturation magnetization is increased.

It is observed that with the increase in copper content in theferrite thin films the coercivity is decreased. It is well known thatcoercivity is linearly related to the reciprocal gain size and it ispossible to tune the magnetic property of polycrystalline hardferrite from hard to soft. Basically, our result is consistent with theAFM micrographs. In fact, with addition of copper in the MgZnferrite, the grain size is increased and consequently, coercivitydecreases.

Fig. 7 shows the dependence of initial permeability withcopper content. From the figure, it is seen that the initialpermeability increases sharply with the increase inconcentration of copper ions. Generally the initial permeabilityis determined by two factors. One is magnetization and theanother is magnetic anisotropy. The magnetic anisotropy field HA

is defined by expressing the magnetic anisotropy energy EA as the

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Fig. 6. (a) Hysteresis loops and (b) variation of magnetic parameters with copper content.

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–30713070

imaginary Zeeman energy of �M HA. Whereas, EA depends on thedirection of magnetization M, and is expressed by the product ofan anisotropy constant K and an even function of sin y, where y isthe angle between M and the easy axis. Consequently, K has thedimension of the anisotropy energy EA, and consequently HA is inproportion to K/M. Therefore, initial permeability becomesapproximately in proportion to M2/K. Since soft ferrite has

spinel crystal structure, the variation of anisotropy constantwith copper could not be the main parameter for affecting on theinitial permeability. On the other hand it is well known that themagnetization mechanism of soft ferrite results from spin rotationand domain wall motion. However, if the grain size is lower than5 mm and the cutoff frequency is lower than 40 MHz, then themain contributor is the grain size. Globus suggested that domain

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Fig. 7. Compositional dependence of initial permeability and susceptibility.

A. Ghasemi et al. / Journal of Magnetism and Magnetic Materials 322 (2010) 3064–3071 3071

walls motion is enhanced with an increase of grain size [35]. Inthe prepared polycrystalline ferrite thin films with the increase ofcopper content the grain size increases whereas the numberof irregular pores decreases. For the samples with lower contentof copper the amount of grain boundaries and porosities are highand consequently the movement of domain wall is more difficultthan the thin film with high concentration of copper. A decreasein the defects by introducing copper in MgZn ferrite not onlyresults in the reduction of demagnetizing field due to thedecreasing of pores but also raise the spin rotationalcontribution, which in turn increases the permeability. Theincrease in initial permeability with the introduction of Cu2 +

ions in MgZn ferrites have been observed by other researchers[36]. From the values of initial permeability, the values of initialsusceptibility at room temperature were calculated using theequation of wint¼(mi�1)/4p and it is observed that this parameterhas similar trend when compared with initial permeability.

4. Conclusions

Nanocrystalline MgCuZn ferrite nanoparticles were preparedby sol–gel method. The TEM micrographs revealed that the sizedistribution of nanoparticles is narrow. The good agreementbetween the experimental data of magnetic susceptibility andVogel–Fulcher model confirms the existence of strong interac-tions between the nanoparticles. The XRD patterns of thin filmsexhibited that spinel phase is formed in all specimens. Atomicforce microscopy showed that nanocrystalline MgCuZn ferritethin films can be successfully prepared by sol–gel method. It isfound that with an increase in copper content, the grain sizeincreases. By incorporating copper ions, the initial permeabilityand saturation magnetization of the samples were increased,while the coercivity decreases.

Acknowledgments

This work was supported in part by Grant-in-Aid for JSPSFellows from Japan Society for Promotion of Science (JSPS) andGrants-in-Aid for Scientific Research (B).

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