NDRO Magnetic Film Memory Mode Using Creep and Boundary Displacement Switching

Abstract

A new switching technique for thin magnetic films of Permalloy was investigated. Orthogonal ac fields were used instead of the usual pulse switching fields. Two variations of the transverse field were tried with ω=2π×10⁶ rad/sec: h_T=H_T½(1−cosωt) and h_T=H_Tsin(ω/2)t. The longitudinal fields (easy direction) were h_L=+H_L cosωt or −H_L cosωt; h_L or −h_L was used depending on which remenant magnetic state of the film was desired. The time display of the vector sum (Liassajou pattern) of h_T and h_L formed a straight line or a parabola for the two transverse drive methods. With the correct combinations of h_T and h_L, the film would switch with both fields applied but would retain the previous state with only one of the two applied. The state of the film was detected by applying the nondestructive h_T and observing the phase of the output from a sense winding. This switching mode appears to have utility in large, word organized memories.