Giant magneto-resistive random-access memories based on current-in-plane devices

Abstract

A Giant Magneto-resistive Random-Access Memory (GMRAM) is a nonvolatile memory consisting of magnetic memory devices integrated with semiconductor electronics. In GMRAMs, magnetic multi-layer devices that exhibit the giant magnetoresistance (GMR) effect, such as "pseudo-spin-valve" (PSV) and "spin-valve" (SV) devices, are used to store information and to allow the data to be read. PSV and SV devices are current-in-plane (CIP) devices that have served as precursors to more recently developed and higher signal memory devices such as current-perpendicularto-plane (CPP) magnetic tunnel junction (MTJ) devices. In this chapter, GMR CIP magnetic device operation and characteristics are described that have supported the demonstration of GMRAMs that have passed nonvolatile data retention tests and complex write and read memory pattern tests at write and read cycle times down to approximately 50 nanoseconds. Write and read characteristics of CIP PSV devices are described in terms of write switching, read switching, resistive, and magnetoresistive properties based on individual and statistical ensembles of PSV devices fabricated on bulk Si as well as CMOS (Complementary metal-oxide-semiconductor) underlayer wafers. Based on experimental work and modeling, magnetization reversal has been inferred to be rotational, including irreversible rotations that correspond to switching, reversible rotations that anticipate switching, and reversible rotations that complete reversal from switching to saturation in the opposite direction. Magneto-resistive and magnetic switching properties along with nonvolatility, nondestructive readout, and potentially unlimited cyclability make PSV and SV devices potential options as nonvolatile memory elements for GMRAMs.