In situ measurements of the coercive force of thin film discs-a comparison of different techniques

Three critical-current detection schemes are compared for demagnetization effects: DC erase, initial pattern: 75 fc/mm: DC erase, initial pattern: 450 fc/mm; reverse DC erase (noise amplitude vs. reverse DC erase current); and amplitude saturation (isolated-pulse amplitude vs. write current). An analysis of the error between the coercivity estimated by the critical current and the coercivity as measured by a vibrating sample magnetometer allows inferences to be made concerning the effect of demagnetizing fields in each of these critical-current detection methods. In most of the cases considered, the demagnetization effects appeared to be independent of the demagnetizating ratio, and may thus be represented by a constant offset term to an otherwise linear relationship between critical current and remanent coercivity. The results obtained with regard to the DC/noise technique are somewhat contradictory with respect to results published by other investigators, but this may be due to the intrinsically low media noise of the CoCrTa media presently used