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InfluenceofHeatTreatmentonStructuralandMagneticPropertiesofManganese-CeriumMixedIronOxideNanocomposites

ARTICLE·SEPTEMBER2015

DOI:10.1166/jap.2015.1184

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ChandrasekarSivakumar

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Journal of Advanced PhysicsVol. 4, pp. 1–5, 2015(www.aspbs.com/jap)

Influence of Heat Treatment on Structural andMagnetic Properties of Manganese-CeriumMixed Iron Oxide NanocompositesS. Chandrasekar1 and E. Ranjith Kumar2,∗

1Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu, India2Sri Ramakrishna Mission Vidyalaya Swami Shivanandha Higher Secondary School,Coimbatore 641020, Tamil Nadu, India

Mn–Ce–Fe–O nanopowder was prepared by evaporation method. The results of XRD clarifying the samplesare having a nanosized particles in the range ∼38–54 nm. SEM was also used to characterize the microstruc-ture of the products. The nanostructure and particle size are confirmed by TEM. The magnetic properties ofMn–Ce–Fe–O system were measured at room temperature by using vibrating sample magnetometer (VSM).It is found that both remnant magnetization (Mr) and saturation magnetization (Ms) decrease with increasingthe annealing temperature due to the decomposition of the system. The high value of saturation magneti-zation (Ms = 48.47 emu/g) and remnant magnetization (Mr = 20.27 emu/g) were obtained only for the as-burnt sample not for annealed samples. The compositional analysis of Mn–Ce–Fe–O system was observed byenergy-dispersive detection X-Ray spectra (EDXS).

KEYWORDS: Nanoparticles, Magnetic Materials, Electron Microscopy.

1. INTRODUCTIONIn recent years, magnetic nanoparticles have been widelystudied because of their excellent and convenient magneticand electrical properties.1�2 Various physical properties ofthe magnetic nanoparticles are greatly influenced by thedistribution of cations among the sublattices, nature ofgrain, grain boundaries, voids, inhomogenetities, surfacelayers, chemical defects, oxygen deficiency and contacts,etc. These magnetic nanoparticles have received greatattention as a result of their magnetic and electronic prop-erties. Such magnetic nanoparticles are currently used inferrofluids,3 microwave devices,4 bioprocessing,5 etc. Themagnetic properties of the nanoparticles can be varied sys-tematically by changing the identity of the divalent cations.It is well known that the chemical, structural and magneticproperties of the nanoparticles are strongly influenced bytheir composition and microstructures, which are sensi-tive to the preparation methods. There are several methodsfor preparing nanosized magnetic nanoparticles such asconventional double sintering technique, co-precipitation,sol–gel, composite-hydroxide-mediated, ceramic methodand chemical route.6–11 Here we used the evaporation to

∗Author to whom correspondence should be addressed.Email: ranjueaswar@gmail.comReceived: 4 February 2015Accepted: 6 February 2015

synthesize Mn–Ce–Fe–O nanoparticles in the range of38∼54 nm. The simple evaporation method in an aqueoussolution containing metal nitrates, deionized water and thenovel use of egg-white proteins as a binder cum gellingmaterial. No other chemicals were added to the solution.This method offers the advantage of simplicity, low cost,environment-friendly and low reaction temperature. Thenature of the prepared sample is in the ferromagneticregion. After annealing the Mn–Ce–Fe–O system could bedecomposed by thermal annealing due to the change ofthe defects. The samples of the Mn–Ce–Fe–O system wereanalyzed by X-ray diffraction (XRD), scanning electronmicroscope (SEM) and energy-dispersive detection X-Rayspectra (EDXS). The effects of annealing temperature onmagnetic properties of the particles are studied using avibrating sample magnetometer (VSM).

2. EXPERIMENTAL DETAILSA simple evaporation method was devised to synthe-size manganese cerium mixed iron oxide Mn–Ce–Fe–Onanoparticles by using egg white with the stoichiome-try (Mn:Ce:Fe:O= 1:1.5:5:10) ratio. The analytical grademanganese nitrate [Mn (NO3�2 ·6H2O], cerium nitrate [Ce(NO3�2 · 6H2O], ferric nitrate [Fe (NO3�3 · 9H2O], andfreshly extracted egg white were used as raw materials.Subsequently, 0.4 M (5.02 g) of manganese nitrate, 0.6 M

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(13.02 g) of cerium nitrate, 2 M (40.4 g) of ferric nitrateand each dissolved in 50 ml of deionized distilled water,were added slowly to the egg white solution with vig-orous stirring at 80 �C to obtain a well-dissolved solu-tion. Throughout the process, no pH adjustment was made.Then, the mixed solution was evaporated by heating at100 �C until a dried precursor was obtained. The precursorwas crushed into powder and the powder was annealed at600 �C and 900 �C for 5 hours in air.The Mn–Ce–Fe–O powder was subjected to XRD

analyses with Rigaku X-ray diffraction unit (ModelULTIMA III) to ascertain crystallinity and determineits structural properties. A scanning electron microscope(SEM with EDX) was used to examine the particle mor-phology, using a JEOL 5600LV microscope at an accel-erating voltage of 10 kV. The magnetic properties of thesamples were investigated by using vibrating sample mag-netometer (Lakeshore VSM 7410).

3. RESULTS AND DISCUSSION3.1. Structural AnalysisFigure 1 shows the XRD pattern of manganese ceriummixed iron oxide Mn–Ce–Fe–O nanopowder preparedby evaporation method. The diffraction patterns of alldiffraction peaks match with the JCPDS card 74-2403 for(MnFe2O4) manganese iron oxide. The X-ray diffractionpatterns show the formation of cubic spinel structures con-tain some secondary XRD reflections, which are due to the

Fig. 1. XRD patterns for particles synthesized at different annealingtemperatures.

CeO2 and Mn2O3 phases (JCPDS 89-8436 and JCPDS 89-4836). The narrow and strong peak indicates the nanocrys-talline nature of annealed samples. Upon annealing, thediffraction peaks become narrower and sharper suggestingthat there is an increase in particle size and crystallinity.The crystallite size can be evaluated from the diffractionpeaks using Scherrer’s formula.

t = 0�9�� cos�

(1)

The lattice parameter (a) has been calculated fromX-ray diffraction data using the formula.12

1d2

= 1a2

�h2+k2+ l2� (2)

The crystalline size (t) and lattice parameter (a) for allthe samples are listed in Table I. From the table, the latticeparameter of the samples is well matched with the standardJCPDS card data. The crystallite size of the samples wasincreased with annealing temperature.

3.2. SEM and EDX AnalysisThe external morphology of the nanocrystalline Mn–Ce–Fe–O system annealed at 900 �C has been visu-alized from the scanning electron micrograph (SEM).From the Figures 2(a)–(c), the SEM photographs ofMn–Ce–Fe–O system clearly show the agglomeration ofprimary nanoparticles to give large and irregular crystals,which may be the effect of preparation method, defects andalso the presence of non-magnetic phases of the system.The compositional analysis of the nanocrystalline Mn–Ce–Fe–O was observed by energy-dispersive detection X-Rayspectra shown in Figure 2(d). From the EDX spectrum,the presence of Ce, Mn, Fe and O is conformed in the sys-tem. The quantitative analysis of EDX spectrum revealedthe relative atomic ratio of Mn–Ce–Fe–O about 1:5:15:10,which is not close to the expected values. It is suggestedthat, the experimental values of the atomic percentagehave some variation with the stoichiometry in preparation.The result of EDX spectrum confirms the unexpected sto-ichiometry, with the appearance of non-magnetic oxideslike CeO2 and Mn2O3.

Table I. Crystal parameters of Mn–Ce–Fe–O system (A-as prepared,B-annealed at 600 �C and C-annealed at 900 �C).

Mn–Ce–Fe–O nanoparticles

Parameters Sample (A) Sample (B) Sample (C)

Particle size (D) nm ∼38 nm ∼45 nm ∼54 nmLattice constant (a) Å 8�42 8�38 8�36Saturation magnetization 48�47 3�44 0�37(Ms) emu/g

Retenivity (Mr) emu/g 20�27 1�63 0�19Coercivity (Hc) G ∼439 ∼432 ∼388

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Fig. 2. SEM morphology and EDX spectrum of Mn–Ce–Fe–O nanoparticles.

3.3. TEM AnalysisParticle size and microstructure of the nanocrystalline Mn–Ce–Fe–O system is visualized through transmission elec-tron microscope (TEM). Figures 3(a) and (b) shows theTEM and SAED pattern of the annealed sample (900 �C)of the system. It clearly shows the inhomogeneous crys-talline structure with few spherical shaped particles.Agglomeration is understood at higher annealing tempera-ture, due to the relative higher annealing temperature and

Fig. 3. TEM image and SAED of Mn–Ce–Fe–O nanoparticles.

interaction between magnetic particles. Also some degreeof agglomeration at higher annealing temperature appearsunavoidable. It reveals that the crystalline sizes of the sam-ple annealed at 900 �C are in the range 40–60 nm, whichis consistent with the results of XRD analysis. Figure 3(B)shows the selected area electron diffraction (SAED) pat-tern of Mn–Ce–Fe–O nanoparticles. The superimpositionsof the bright spots indicate the good crystalline nature ofthe samples with equal lattice arrangement.

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Fig. 4. VSM study of Mn–Ce–Fe–O nanoparticles; (a-as-prepared); (b-annealed at 600 �C); (c-annealed at 900 �C).

3.4. Magnetic PropertiesFigure 4 shows the M–H loops for the as-prepared andannealed samples of Mn–Ce–Fe–O nanoparticles preparedby evaporation method. It is observed that all the sam-ples exhibit magnetic properties like coercivity, saturationmagnetization, retenivity etc., these are listed in Table I.It is found that the saturation magnetization and reteniv-ity decreases with increasing the annealing temperaturedue to decomposition of the system.13 For as-preparedsample, saturation magnetization (Ms) is approximately48.47 emu/g and this value decreases to about 0.37 emu/g.The remnants magnetization (Mr) for the as-prepared sam-ple is about 20.27 emu/g and it reduces to 1.63 emu/gafter annealing at 600 �C and further decreases to about0.19 emu/g after annealing the sample at 900 �C. Thedecrease of Ms and Mr suggest the decrease of defectsor/and increase of grain size or/and surface change or/andrelaxing of internal stress introduced during mixed, i.e.,the improvement of the crystallinity.14–16

4. CONCLUSIONThe structural and magnetic properties of nanosized Mn–Ce–Fe–O system was studied and obtained results were

analyzed. Indexed powder XRD pattern revealed thatthe samples prepared by this route were Mn–Ce–Fe–Onanoparticles with cubic spinel structure. It was seen thatthe particle size of synthesized Mn–Ce–Fe–O samples wasin the range of ∼38–54 nm. The morphology of the Mn–Ce–Fe–O sample is visualized by SEM. The EDX spec-trum confirms the presence of Ce, Mn, Fe and O in thesystem. The TEM image clearly showed the nanostructureof the system. The saturation magnetization and rem-nants magnetization decreases with increasing the anneal-ing temperature.

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