Magnetocrystalline Anisotropy of M-Type Sr-Ferrite Containing Lanthanum and Cobalt

Abstract

The magnetic anisotropy constant K₁ and anisotropy field H_A of M-type Sr-ferrite containing La and Co (Sr_0.7La_0.3Fe_11.7Co_0.3O₁₉) were investigated by the singular-point detection (SPD) method using a pulsed field and SQUID magnetometers, and also by torque measurements. The value of H_A=22.2 kOe was obtained by the SPD method at 298 K. The K₁ value was 4.2 × 10⁶ erg/cm³ at 298 K, which was determined by extrapolation to the high field of the coefficient of the sin(2 φ) term calculated by Fourier analysis of unsaturated torque curves. This value was 15% larger than that of conventional Sr-ferrite (SrFe₁₂O₁₉) in the temperature range from 77 to 373 K.