Determination of anisotropy fields in recording media

This work describes an experimental study which reviews the various techniq ues that can be used for determination of anisotropy fields in recording me dia. At the present time this topic is of considerable importance due to th e need to understand the detailed mechanisms of magnetization reversal and the factors that control the switching field distribution in recording medi a. We have used a metal-particle-based tape material and have employed vari ous magnetic techniques for the determination of the apparent anisotropy fi eld, H-K. The techniques included hysteresis loops measured in a direction transverse to the texture direction of the tapes, single-point detection in the successive derivatives of the magnetization with respect to the field, transverse susceptibility measurement, and the variation of the bulk coerc ivity with temperature. We find the temperature variation of coercivity pro duces values of H-K far smaller than values determined by other methods due to orientation effects. General agreement is seen for the other techniques mentioned and results for samples with differing degrees of texture show t hat the apparent anisotropy field of the grains as measured by these techni ques is influenced greatly by orientation effects. (C) 2000 American Instit ute of Physics. [S0021-8979(00)84008-6].