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

Abstract

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 S_w=(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.