ARTICLE Copyright © 2013 by American Scientific Publishers All rights reserved. Printed in the United States of America Journal of Nanoengineering and Nanomanufacturing Vol. 3, pp. 1–8, 2013 (www.aspbs.com/jnan) Structural, Dielectric, AC Conductivity, and Magnetic Properties of Cr 3+ Substituted Ni–Mg Ferrite Nanoparticles Mohd. Hashim 1 ∗ , Alimuddin 1 , Shalendra Kumar 2 , Sagar E. Shirsath 3 , E. M. Mohammed 4 , and Ravi Kumar 5 1 Department of Applied Physics, Aligarh Muslim University, Aligarh, 202002, India 2 Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea 3 Department of Information Engineering, Spin Device Technology Centre, Shinshu University, Nagano 380-8553, Japan 4 Department of Physics, Maharajas College, Ernakulam 682011, Kerala, India 5 Centre for Material Science Engineering, National Institute of Technology, Hamirpur, HP, India ABSTRACT Series having composition, Ni 0.5 Mg 0.5 Fe 2−x Cr x O 4 (0 ≤ x ≤ 10) were successfully made by citrate-gel auto com- bustion method and characterized by means of various techniques. The formation of single phase cubic spinel structure was confirmed by X-ray diffraction psychotherapy. Infrared spectroscopic studies revealed two main absorption bands in the range 400–800 cm −1 arising due to tetrahedral (A) and octahedral (B) stretching vibra- tions. In order to understand the morphology and grain shape FE-SEM study has been carried out. The content of the metals in the resulting spinel ferrites are close to the theoretical values as shown by EDX measurements. A qualitative explanation is given for the composition dependence of dielectric parameters. From the dielec- tric studies on the systems it is possible to correlate a relationship between the polarization and conducting mechanism with the nickel magnesium ferrite nanosystems. The M–H loop of as synthesized samples has been traced using the Vibrating Sample Magnetometer (VSM) and magnetic parameters such as saturation magnetization (M S ), coercivity (H C ) and remanence (M R ) are obtained from VSM data. KEYWORDS: Polycrystalline Ferrites, Dielectric Constant, Effect of Additives, Magnetism. 1. INTRODUCTION Recently, micro scale and nanoscale materials have strained an immense attention and enthused rigorous researches because of their potential high-tech applica- tions. Among the various classes of nanomaterials, metal oxides (ferrites) are the common, most diverse and pos- sess richest class in terms of physical, chemical and struc- tural properties. As a result, various applications of metal oxides, such as fabrication of microelectronic circuits, sen- sors, piezoelectric devices, fuel cells, dielectrics, lasers, magnets and catalysts have been discussed. Both perme- ability and coercivity can be tailored to use in radio, television, satellite communication, bubble devices, digital recording, permanent magnets, medical and bio-inspired technologies. They have relatively high resistivity, excel- lent magnetic property at carrier frequencies and suf- ficiently low losses for microwave application such as ∗ Author to whom correspondence should be addressed. Email: md.hashim09@gmail.com Received: xx Xxxx Xxxx Accepted: xx Xxxx Xxxx circulators, insulators and phase shifters. 1–5 These prop- erties of ferrites are strongly dependent on their method of preparation, chemical composition, sintering tempera- ture, doping additives, grain size etc. 6 Recently, substan- tial attempt has been made on the surface modification of nanoparticles and the preparation of different type of metal oxides. Various methods are available for the syn- thesis of metal oxides, such as microwave refluxing, sol– gel, hydrothermal, co-precipitation, citrate-gel and spray pyrolysis 7–8 etc. The assortment of suitable synthetic pro- cedure often depends on the desired properties and final applications. Among these synthesis techniques, citrate- gel auto combustion method has several advantages over others for preparation of nano sized metal oxides as the process begins with a relatively homogeneous mixture and involves low temperature conditions resulting in a uni- form ultrafine porous powders. Therefore, we have decided to make Ni 05 Mg 05 Fe 2−x Cr x O 4 ferrite by citrate-gel auto combustion. Commonly metal ions used for enhancing the properties of spinel ferrites are Ni, Mg, Mn, Zn, Ti, Co, Cu, Mg, etc. Khalid et al. have been reported the finite size effect and influence of temperature on electrical J. Nanoeng. Nanomanuf., 3, 1–8, 2013 2157-9326/2013/3/001/008 doi:10.1166/jnan.2013.1108 1