Characteristics of magnetic properties of substituted hexagonal ferrites

Abstract

The samples of barium hexaferrite BaFe12-2x(Me1Me2)xO19 with x from 0.0 to 0.6 were prepared by various methods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ions and their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain size and high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal is to reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magnetic properties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m and remanence Js–r increased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. The steep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m–1.oC–1) for the Co-Zr substitutions and positive for the rest of samples.