Angular variation of the coercivity in anisotropic barium and strontium ferrite permanent magnets

Room-temperature measurements have been made of the variation of the intrinsic coercivity Hc of anisotropic barium ferrite and strontium ferrite permanent magnets as a function of the angle θ between the direction of measurement and the preferred axis of magnetization. For the strontium ferrite specimen the angular variation Hc vs θ was also measured at 77, 130, and 230 K. All the results showed a gradual increase in Hc with increase in θ up to a maximum and thereafter a rapid decrease to Hc=0 at θ=90°. The angular variation in coercivity was also measured after saturation parallel to the direction of measurement. An attempt has been made to interpret the results.