Internal Field Distribution in Keepered and Nonkeepered Permalloy Film Memories

Abstract

The magnetic field distribution inside an 80–20 Ni–Fe Permalloy layer is a major contributing factor to the adjacent bit interference effect limiting the maximum permissible packing density of a high-speed main memory. The internal field distribution Hi (z) is calculated using the concept of magnetic charge distribution and Stoner-Wohlfarth switching model. The results are plotted for various driving field distribution and magnetic film magnetization parameters. The data are obtained with the aid of an iterative computer-program solution for small volumes [(δM/Hk) <10−5m] and with an inverse matrix computer solution for large values of (δM/Hk) (δ=film thickness). These techniques are further extended to the treatment of magnetic keepers and their effect on adjacent bit interference. The calculated data are compared with experimental results and the agreement is found to be very close.