IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 42 (2009) 165007 (7pp) doi:10.1088/0022-3727/42/16/165007 Comparison of initial permeability of MgCuZn ferrites sintered by both conventional and microwave methods W Madhuri 1 , M Penchal Reddy 1 , N Rammanohar Reddy 1 , K V Siva Kumar 1,3 and V R K Murthy 2 1 Ceramic Composite Materials Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur-515 003, India 2 Microwave Laboratory, Department of Physics, Indian Institute of Technology, Chennai-600 036, India E-mail: sivakumar.sivani@gmail.com Received 26 February 2009, in final form 22 May 2009 Published 31 July 2009 Online at stacks.iop.org/JPhysD/42/165007 Abstract NiCuZn ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like low magnetostriction, environmental stability, low stress sensitivity and low cost. In view of this, a series of non-stoichiometric MgCuZn ferrites (Mg 0.5−x Cu x Zn 0.5 Fe 1.9 O 4−δ with x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25) have been successfully synthesized by both conventional and microwave sintering techniques. The non-stoichiometry was intentionally introduced into the ferrites to ensure high resistivity of the samples. X-ray diffraction patterns confirm the single phase spinel structure in both cases. The elemental composition of these ferrites was analysed by energy-dispersive x-ray spectrometry. The samples sintered by the microwave technique were found to be denser than the conventionally sintered samples. The initial permeability of MgCuZn ferrites was studied with an increase in copper concentration from x = 0.0 to 0.25. The temperature variation of the initial permeability of these samples was carried out from 30 ◦ C to 150 ◦ C. The results are discussed in the light of microstructure variations of the conventionally and microwave sintered samples. The phenomena involved in microwave sintering are also discussed. (Some figures in this article are in colour only in the electronic version) 1. Introduction Spinel ferrites find potential applications in electrical components, memory devices, magnetostrictive devices and microwave devices over a wide range of frequencies because of their high resistivity and low losses [1]. Generally NiCuZn ferrites are used for multilayer chip inductor applications (MLCI). This is due to their better electromagnetic properties [2, 3]. MgCuZn ferrite is also a pertinent magnetic material with a wide range of applications owing to its superior properties such as high resistivity, low magnetostriction, fairly high Curie transition temperature, environmental stability and low cost [4–12]. As the magnetostriction of MgCuZn ferrite [11] is lower than that of NiCuZn ferrite it would show less 3 Author to whom any correspondence should be addressed. stress sensitivity compared with that of chip inductors made out of NiCuZn ferrites [13]. Use of microwave energy for synthesis and processing of materials is an exciting new field in material science with enormous potential for synthesizing new materials and novel microstructures [14, 15]. The growing interest during the past decade is essentially due to the possibility of a reduction in manufacturing cost on account of energy savings, high energy efficiency, shorter processing times and improved product uniformity and yields [16]. The essential difference in the conventional and microwave sintering processes is in the heating mechanism. In conventional sintering, heat is generated by external heating elements and then it diffuses into the test sample via radiation, conduction and convection producing high 0022-3727/09/165007+07$30.00 1 © 2009 IOP Publishing Ltd Printed in the UK