Conference Proceedings Vol. 50
“ICAME-95”
I. Ortalli (Ed.)
SIF, Bologna 1996

P. Wartewig, M.K. Krause, S. Rösler, R. Sonntag

Abstract

Our investigation of ZnTi substituted barium hexaferrite samples shows an increased saturation magnetization for low substitution rates. The increase results from the strong preference of the Zn ions for the tetrahedral 4f₁ sublattice and the small degree of spin canting compared to other substituted hexaferrite samples.

Introduction

M-type barium ferrite, BaFe₁₂O₁₉, is one of the most important hard magnetic materials and is widely used for permanent magnets and magnetic recording media. The regular barium hexaferrite has a magnetoplumbite structure (space group P6₃/mmc). The iron ions occupy five different sites in the lattice with three different coordinations (tetrahedral, octahedral and fivefold). The magnetic structure was described for the first time by Gorter [l] on the basis the indirect exchange theory. The magnetic moments of the iron ions are arranged parallel to the hexagonal c-axis, but with two opposite spin directions of the iron sublattices (three spin up sublattices, two spin down sublattices). The resulting magnetic structure is ferrimagnetic with a Curie temperature of T_c=720K for the pure BaFe₁₂O₁₉. Much work has been done to change the magnetic properties by a substitution of the Fe³⁺ ions by other cations [2]. The goal of such studies was to obtain an increased saturation magnetization. However, this has never been reported in the literature.