Magnetic Materials for Digital Computer Components. II. Magnetic Characteristics of Ultra-Thin Molybdenum-Permalloy Cores

Measurements of the flux-reversal time τ as a function of the applied magnetic field H have been made for ⅛-mil, ¼-mil, ½-mil, and 1-mil 4–79 molybdenum-Permalloy tape cores. There measurements have been taken at seven temperatures, ranging from −196°C to 270°C. From these measurements, the switching coefficient Sw=(H−H0)τ is found, where H0 is the threshold field value for irreversible domain-wall motion. Determination of the switching coefficient as the tape thickness is varied permits a separation of the spin-relaxation and eddy-current contributions 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 H0 are approximately halved, and the spin-relaxation contribution is reduced by 20 percent. All these factors lead to a faster flux reversal at higher temperature for a given applied field. This behavior is in agreement with theoretical predictions.