Research Article Effects of Milling Atmosphere and Increasing Sintering Temperature on the Magnetic Properties of Nanocrystalline Ni 0.36 Zn 0.64 Fe 2 O 4 Abdollah Hajalilou, 1 Mansor Hashim, 1 Halimah Mohamed Kamari, 2 and Mohamad Taghi Masoudi 3 1 Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 2 Physics Department, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 3 Department of Materials Engineering, Islamic Azad University, Najafabad Branch, Isfahan, Iran Correspondence should be addressed to Abdollah Hajalilou; e.hajalilou@yahoo.com Received 6 October 2014; Revised 17 March 2015; Accepted 19 May 2015 Academic Editor: Mohamed Bououdina Copyright © 2015 Abdollah Hajalilou et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Nanocrystalline Ni 0.36 Zn 0.64 Fe 2 O 4 was synthesized by milling a powder mixture of Zn, NiO, and Fe 2 O 3 in a high-energy ball mill for 30 h under three diferent atmospheres of air, argon, and oxygen. Ater sintering the 30 h milled samples at 500 ∘ C, the XRD patterns suggested the formation of a single phase of Ni-Zn ferrite. he XRD results indicated the average crystallite sizes to be 15, 14, and 16 nm, respectively, for the 30 h milled samples in air, argon, and oxygen atmospheres sintered at 500 ∘ C. From the FeSEM micrographs, the average grain sizes of the mentioned samples were 83, 75, and 105nm, respectively, which grew to 284, 243, and 302 nm ater sintering to 900 ∘ C. A density of all the samples increased while a porosity decreased by elevating sintering temperature. he parallel evolution of changes in magnetic properties, due to microstructural variations with changes in the milling atmosphere and sintering temperature in the rage of 500–900 ∘ C with 100 ∘ C increments, is also studied in this work. 1. Introduction Ni-Zn ferrite is a sot magnetic ceramic that has spinel coniguration in terms of a face-centered cubic lattice of the oxygen ions, with the unit cell consisting of 8 f.u. of the type (Zn  Fe 1− ) [Ni 1− Fe 1+ ]O 4 . In this formula the metallic cations in round bracket occupy the tetrahedral A sites and the metallic cations in square bracket occupy the octahedral B sites [1]. Ni-Zn ferrites are important ceramic-magnetic materials in our daily lives due to their extensive use in elec- trical devices. Due to their unique characteristics such as low eddy current loss, good thermal and chemical stability, and high Curie temperature [2, 3], they are also found in a wide variety of applications. Such applications include being used in microwave devices, rod antennas, power transfer systems, and read/write heads for high speed digital tapes. Several studies have reported the dependence of magnetic properties of Ni-Zn ferrites on their microstructure, chemical compo- sition, sintering temperature, and preparation method [4–6]. Many researchers, including but not limited to [3, 6–9], have investigated the production of Ni-Zn ferrites via high-energy ball milling as well as the relationship between their magnetic properties, variations in their sintering temperature, com- position, and certain other parameters. To the best of our knowledge, no research has been carried out to investigate the efects of a milling atmosphere on the magnetic properties of these ferrites. herefore, the present study was designed to investigate the efects of milling atmospheres including air, argon, and oxygen on the magnetic properties of Ni-Zn ferrite with the less known composition of Ni 0.36 Zn 0.64 Fe 2 O 4 sintered at temperatures ranging from 500 to 900 ∘ C. Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 615739, 11 pages http://dx.doi.org/10.1155/2015/615739