Size dependence of switching thresholds for pseudo spin valve MRAM cells

Abstract

For magnetoresistive random access memory (MRAM) to be a successful new memory technology, very dense cells with high output are necessary. As bit sizes shrink, it becomes advantageous to employ memory modes in which the uniaxial anisotropy lies along the length of the bit. For bits smaller than approximately 0.2 μm in width, curling across the bit becomes small, and the magnetization may be treated as a uniform single domain. We have modeled “pseudo spin valve” MRAM cells in the single-domain approximation. Calculations in this size regime for asymmetric giant magnetoresistive (GMR) sandwich material reveal that switching thresholds are sensitive to bit size. Submicron cells 0.4 μm×2.2 μm in size have been patterned from asymmetric GMR sandwich material and switching thresholds compare favorably with the single-domain model. These “pseudo spin valve” memory cells are very promising for nonvolatile, high speed, high-density memories.