Effects of Tape Thickness and Temperature on Flux Reversal of 4-79 Molybdenum-Permalloy

Abstract

Measurements of the flux reversal time t have been made for 1/8-mil, 1/4-mil, 1/2-mil, and 1-mil 4-79 Molybdenum-Permalloy tape cores as a function of the applied field. These measurements were taken at seven different temperatures, ranging from -196ºC. to 270ºC. From these measurements, the switching coefficient S[subscript W] = (H - H[subscript O] t is found. Determination of the switching coefficient as a function of tape thickness is shown to permit a separation of the spin-relaxation and eddy-current contribution to switching delay. These contributions are studied individually as functions of temperature. Upon increasing the temperature over the range considered, the eddy-current contribution and the threshold field value H[subscript O] are approximately halved while the spin-relaxation contribution is reduced by 20%. All these factors lead to a faster flux reversal at higher temperatures. This behavior is show to be in agreement with theoretical predictions.