Single-domain model for toggle MRAM

An overview is presented of the use of a single-domain model for developing an understanding of the switching of two coupled magnetic free layers for toggle MRAM (magnetic random access memory). The model includes the effects of length, width, thickness, magnetization, thickness asymmetry, intrinsic anisotropy, exchange coupling, dipole coupling, and applied magnetic field. First, a simple perturbative approach is used to understand the basic phenomena at low fields, including the critical switching curve and activation energy. Then the more general model is applied in order to understand the effects of saturation at large field, and thickness asymmetry. The major results are that toggle MRAM should have a larger margin for half-select and full-select switching fields than Stoner-Wohlfarth MRAM, and that the activation energy should increase upon half-select, thus eliminating the half-select activated-error problem. ©Copyright 2006 by International Business Machines Corporation.