Magnetic Properties of W-Type Hexaferrite Powders

Abstract

An investigation was undertaken to elucidate the preparation conditions and magnetic properties of W-type hexaferrite powders with the formula AM₂Fe₁₆O₂₇ (A=Ba or Sr, M=Fe²⁺, Zn+Cu, Zn+Cd, Zn+Mg). A pure W-phase was formed by firing a mixture of carbonates and oxides in the appropriate molar ratio at 1200^° ∼1400^°C in an atmosphere of P O₂ /(P O₂ +P N₂ )=10^-2 ∼10^-6 or in air. The values σ_s=70 ∼79 emu/g, H _c=400 ∼2000 Oe, σ_r/σ_s ∼0.90 and T _c=350^° ∼500^°C were obtained for the oxide powders, aligned along the c axis.