Comments on "Improving accuracy of intrinsic coercivity measurement for magnetically soft materials"

Abstract

The authors of paper by Hilton et al. (see ibid., vol. 41. no. 8, P.2322-7, Aug. 2005) conclude among other things that the commercial imperative is to obtain accurate coercivity results. How slow does magnetizing field decay have to be in order to achieve this? There is no universal answer; it depends on material and on dimensions. For routine coercivity measurement of soft iron bars, a 60-s linear ramp time is advised. This protocol allows accurate coercivity measurement within an acceptable amount of laboratory time. The present author would like to mention that years ago a number of experiments were carried out indicating that coercivity of magnetically soft materials depends strongly on rate of rise of driving field. In case of a linear ramp driving held, coercivity, depends linearly on square root of this rate of rise, k/sub i/. It was shown experimentally that above dependence holds also for soft ferrites and Permalloy cores as well as for magnetic thin films.