ELSEVIER Journal of Magnetism and Magnetic Materials 172 (1997) L9-Lt4 -__1-__-m--1. AHI $!g$& Al iLllc Al IAerIals --_---_--- -- Letter to the Editor Microstructural dependence of the magnetic properties of sintered NiZn ferrites from hydrothermal powders Anderson Dias”**, Roberto Luiz Moreirab, Nelcy D.S. Mohallemb, AbB Israel C. Persianob a Departamento de Engenharia Metallirgica e de Materiais. EE-UFMG, Rua Espirito Santo 3SISala 206. 3016&036 Belo Horizonte. MG, Brazil bDepartamentos de Fikica e Quimica, ICEx-UFMG, CP 702, 30161-970, Belo Horizonte, MG, Brazil Received 25 March 1997 Abstract The magnetic properties after sintering of Nio,34Zno,60Fez,0604 from hydrothermal submicrometer-sized powders were evaluated. The results from hysteresis magnetic loops showed high saturation magnetization (5000 < 4rcM, < 7000 G), low remanence (160 < 4nM, < 300 G) and coercitivity (22 < H, < 35 Oe) values. The microstructural evolution was correlated to the magnetic parameters and the relations between them were discussed. The absolute values of saturation were compared to other NiZn ferrites of similar composition and obtained from different methods described in the literature. PACS: 75.50.Gg; 81.40.R~; 81.20.E~; 81.20.Ka Keywords: Hydrothermal process; NiZn ferrites; Magnetic properties; Solid-state sintering; Microstructure 1. Introduction Magnetic ceramics, usually represented by fer- rites, are becoming increasingly important mate- rials for electronic components. Since the largest increase in ferrite use has come from the area of power magnetics [ 11, this area seems to be the most *Corresponding author. E-mail: atelier@gold.com.br; fax: + 55-31-238-1815. receptive to new technological improvements. For instance, the range of ferrites from Siemens Matsushita Components is based solely on mag- netically soft substances [2]. From these, the ap- propriate ferrite cores are produced for a large variety of inductive components. They include cores for filters, broad-band applications and power transformers used in professional switched- mode power supplies. In the last few years, a significant advance in circuit miniaturization was achieved by the em- ployment of the economic flat design (EDF) power 0304-8853/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PII SO304-8853(97)00134-O