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 AM 2 Fe 16 O 27 (A=Ba or Sr, M=Fe 2+ , 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 O 2 /( P O 2 + P N 2 )=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.