Determination of thin film media model parameters using DPC imaging and torque measurements

Abstract

A micromagnetic model consisting of coupled hexagonal grains has been used to investigate the remanent-state ripple structure, the expected torque, and the rotational hysteresis behavior of thin magnetic films. The parameters of the model are the anisotropy field, the magnetostatic coupling, and the phenomenological exchange coupling between grains. The scale of the ripple pattern as measured by Lorentz microscopy using the differential phase contrast imaging technique can be used to fix the model parameters unambiguously, under the assumption that the parameters have fixed single values. Experimental rotational hysteresis curves cannot by fitted in detail without assuming a fairly broad distribution of anisotropy fields. It should be possible, given both kinds of data on a single sample, to determine the exchange coupling and average anisotropy field as well as a distribution of anisotropy fields which fits the width of the rotational hysteresis curve. >