The angular dependence of the remanent coercivity of gamma ferric oxide `tape´ particles

Samples containing dilute dispersions of partially aligned gamma ferric oxide tape particles have been magnetized to near saturation along the alignment axis. By applying progressively higher alternating fields (AFs) at a given angle to the alignment axis, the saturated isothermal remanent magnetization (IRM) can be gradually destroyed and the peak field required to reduce the IRM to half its original value can be found. If this process is repeated for different angles, the angular variation of coercivity of remanence of an average single aligned particle can be obtained by extrapolating the results to the case of perfect alignment. The results show that the remanent coercivity increases as the angle which the AF makes with the alignment axis increases, thus supporting the conclusion of J.E. Knowles (1978) who obtained similar results by carrying out experiments on individual particles