Structural and Magnetic properties of Ni 0.5 Zn 0.5 Al x Fe 2x O 4 nano ferrite system B. Rajesh Babu a , M.S.R. Prasad b , K.V. Ramesh c, * , Y. Purushotham d a Dept. of Physics, G.V.P. College of Engineering for Women, Visakhapatnam, India b Dept. of Physics, MVGR College of Engineering, Chintalavalasa, Vizianagaram, India c Dept. of Physics, GIT, GITAM University, Rushikonda, Visakhapatnam, India d Centre for Materials for Electronics Technology (C-MET), Cherlapally, Hyderabad 500 051, India highlights  Al 3þ substituted nanocrystalline NieZn ferrites are with single phase spinel structure.  Al 3þ ions are distributed into tetrahedral and octahedral sites is confirmed from IR studies.  The lattice constant decreases with increasing of Al 3þ ion concentration due to the replacement of Fe 3þ ions.  The M s value decreases from 70.53 emu gm 1 to 40.19 emu gm 1 with the increase of Al 3þ .  Decrease in M s due to non-collinear and canted spin structures present in BeB sites. article info Article history: Received 29 March 2014 Received in revised form 2 August 2014 Accepted 9 August 2014 Available online 5 September 2014 Keywords: Magnetic materials Chemical synthesis DebyeeScherrer powder method Infrared spectroscopy Magnetometer Electron microscopy abstract Nanocrystalline Nickel Zinc ferrites of composition Ni 0.5 Zn 0.5 Fe 2x Al x O 4 (where x ¼ 0.00e0.25) have been synthesized by the nitrate citrate auto combustion technique. These samples were sintered at 1000  C. All the samples were characterized by XRD, Infrared spectroscopy (IR), Scanning Electron Microscopy (SEM) and Vibrating sample magnetometer (VSM). The XRD patterns confirm the spinel structures. The lattice constant decreases with increasing aluminum concentration which is due to the replacement of Fe 3þ with Al 3þ ions. Cation distribution proposed from XRD and IR. It is observed that Al 3þ ions are distributed into tetrahedral and octahedral sub-lattices. The saturation magnetization decreases from 70.53 emu gm 1 to 40.19 emu gm 1 with the increase of aluminum. This decrease in magnetization is ascribed to the presence of the non-collinear spin (canted spin) structure in octahedral sub-lattice. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Nanocrystalline spinel ferrites are technologically important materials and have large number of applications from microwave to radio frequencies. Among many available ferrite systems, MneZn and NieZn ferrites are abundantly used as core materials in various electromagnetic devices. Of these, NieZn ferrites plays a key role in wide range of applications such as low and high frequency trans- former cores, antenna rods and microwave devices due to their high resistivity and, therefore low eddy current losses, high saturation magnetization, high Curie temperature, low dielectric losses, relatively high permeability, and chemical stability [1e3]. It is well known that Ferrites possess cubic closed packed arrangement of oxygen ions. The elementary unit cell comprises eight molecules of AB 2 O 4 in which 32 oxygen ions form cubic close packed structure leaving 96 available interstitial sites. Out of these 96 interstitial sites, 64 are tetrahedral and 32 are octahedral sites, customarily designated as A and B sites respectively; 8 of the A sites and 16 of the B sites are occupied by cations in the stoichiometry spinel. The magnetic and electrical properties of these ferrites depend upon the type of the metal cations and their distribution among the two interstitial sites in A & B sub lattices. A precise knowledge of cation distribution over the crystallographic sites is essential to understand the behavior of the spinel ferrites. It is well known that when the ferrites are sufficiently diluted with non- * Corresponding author. E-mail addresses: kvramesh11@gmail.com, kv_ramesh5@yahoo.co.in (K.V. Ramesh). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys http://dx.doi.org/10.1016/j.matchemphys.2014.08.019 0254-0584/© 2014 Elsevier B.V. All rights reserved. Materials Chemistry and Physics 148 (2014) 585e591