Determination of the Anisotropy in Thin Permalloy Films

Abstract

Four types of measurement on thin Permalloy films are discussed which in the coherent‐rotation theory yield equivalent values for the anisotropy field H_k: (A) Hysteresis loop; (B) high field torque; (C) rotational hysteresis; (D) torque 90° to the easy axis. Results reported for several films show that the values obtained from (A) and (B) agree reasonably well, while the values from (C) and (D) are found to be too high and too low, respectively. These discrepancies are explained in terms of a dispersion in both the magnitude and direction of the anisotropy. A torque method to determine an effective dispersion is outlined and illustrated for a particular case.