Size dependent electrical and magnetic properties of ZnFe 2 O 4 nanoparticles synthesized by the combustion method: Comparison between aspartic acid and glycine as fuels A. Shanmugavani a , R. Kalai Selvan a,n , Samar Layek b , C. Sanjeeviraja c a Solid State Ionics and Energy Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore 641046, India b Department of Physics, Indian institute of Technology, Kanpur 208016, India c Department of Physics, Alagappa Chettiar College of Engineering and Technology, Karaikudi- 630 004, Tamil Nadu, India article info Article history: Received 12 September 2013 Received in revised form 5 November 2013 Available online 26 November 2013 Keywords: Zinc ferrite Nanoparticle Impedance Conductivity VSM Mössbauer spectroscopy abstract Using two different fuels such as aspartic acid and glycine, the spinel zinc ferrite nanoparticles were synthesized by the combustion method at different pH values. The thermochemical calculations for both the fuel assisted materials and its adiabatic flame temperature were calculated. The X-ray diffraction (XRD) pattern revealed the formation of single phase ZnFe 2 O 4 with high crystallinity. The characteristic functional groups of Fe–O and Zn–O were identified through FTIR analysis. Uniform size distribution of spherical particle in the average size range of 35–100 nm was inferred from SEM images. The room temperature DC conductivities of ZnFe 2 O 4 particles prepared by using aspartic and glycine are in the order of 10 À7 and 10 À8 respectively. The dielectric spectral analysis inferred that the obtained dielectric constant is high at low frequency and decreases with increase in frequency. This dielectric behavior is in accordance with the Maxwell–Wagner interfacial polarization. VSM and Mössbauer analysis revealed that the prepared material exhibits paramagnetic behavior and Fe 3 þ state of iron content in ZnFe 2 O 4 at room temperature. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Divalent metal ion substituted magnetite, Fe 3 O 4 materials such as MFe 2 O 4 (MQZn, Co, Ni, Cu, Mn) finds tremendous applications in various technological platforms due to its remarkable electrical and magnetic properties. Among the spinel ferrite, ZnFe 2 O 4 is well explored because of its marked magnetic properties in nanore- gime than its bulk counterparts. It has a normal spinel structure with Zn (II) ions in the tetrahedral site and Fe (III) ions in the octahedral site. Further, this has been used in magnetic materials [1], semiconductor photocatalysis [2,3], ferrofluid technology [4], hot-gas desulfurization [5,6] and gas sensors [7] and so on. It is well known that the cation distribution and grain size mainly affects the magnetic and electrical properties of the ferrites [8]. There are reports showing clear evidence that the bulk ZnFe 2 O 4 material exhibits paramagnetic behavior at room temperature and shows antiferromagnetic behavior at a Neel temperature of 10 K [9]. Ultrafine particles exhibit cationic inversion and the percen- tage of occupancy of Zn 2 þ ions depending on the method employed to synthesize nanoparticles [10–12]. Similarly, ZnFe 2 O 4 nanoparticles have been prepared by various methods including co-precipitation [13], micro-emulsion [14], ball milling [15], ultra- sonic cavitation [16], hydrothermal [17] etc. Generally, for the preparation of metal oxides by the combus- tion method, metal nitrates and organic fuels are used as oxidizers and reducing agents respectively. During combustion reaction they produce highly self-sustaining exothermic reaction. The main advantage of the combustion method includes the chemically homogenous products, ease of preparation, low energy loss, feasibility for large-scale production and high purity final pro- ducts. Further, the combustion reaction mainly depends upon the choice of fuel and the oxidizer to fuel ratio, since it liberates maximum amount of heat energy based on the reducing power of the fuel [18]. Mostly, urea [19], citric acid [20], polyvinyl alcohol [21], glycine [22] and ethylene glycol [23] have been used as fuels for the preparation of spinel ferrites by combustion synthesis. However, urea [24–26], citric acid [27], glycine [28], oxalyl dihy- drazide [29], thiourea [30] have been used as fuels for the synthesis of ZnFe 2 O 4 nanoparticles. Even though, scarce amount of works are available on the synthesis of ZnFe 2 O 4 nanoparticles by combustion methods [13–17, 24–30], here we have used two different fuels such as aspartic acid and glycine and the reactions are carried out in three different pH values in order to vary the physico-chemical properties. It is well Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jmmm.2013.11.018 n Corresponding author. E-mail address: selvankram@buc.edu.in (R. Kalai Selvan). Journal of Magnetism and Magnetic Materials 354 (2014) 363–371