Anisotropy Field Distribution measurements for thin film media

Summary form only given. The methods used for measuring the Anisotropy Field Distribution (AFD) could be classified into switching (involving irreversible magnetization processes, e.g. Rotational Hysteresis Loss) and stiff (involving reversible processes, e.g. hard axis loop). Because the irreversible processes are thermally activated, the switching fields and consequently the H/sub K/ values measured by switching methods are decreased with respect to their intrinsic values because of thermal relaxation. The goal of this work is to explain the difference between the AFDs measured by switching and stiff methods for both, longitudinal and perpendicular recording media. Using the Maximum Entropy Method, it is shown that the almost two times lower values for H/sub K/ obtained for CoCrPtB-type longitudinal thin films (hard disk media) by switching methods with respect to those given by stiff methods are due to thermal relaxation. Particle interactions are shown to act only on the width of the AFD, without affecting the position of its maximum. Better agreement between the AFDs found using switching and stiff methods was obtained for perpendicular than for longitudinal media, that was interpreted as the effect of both, the high texturing degree and the higher stability factor for the perpendicular medium. In order to correct the AFD obtained by switching methods for the effects of thermal relaxation, one needs an estimation of the particle switching volume V/sub SW/. In this work, a new model for estimating V/sub SW/ using the field sweep rate dependence of coercivity H/sub C/(R) is described. The results regarding H/sub K/ and KV/(k/sub B/T) given by the proposed model are compared with those obtained using the time dependence of coercivity H/sub C/(t) and remanence coercivity H/sub RC/(t) and good agreement is obtained for both, longitudinal and perpendicular media.