Thermally stable multistate characteristics in multidomain-driven magnetic tunnel junctions

Abstract

The intermediate resistance states observed between the P and AP states of magnetic tunnel junctions (MTJs) have traditionally been considered detrimental to device reliability. This work evaluates a multidomain manipulation approach that transforms these intermediate states into controllable multistate storage resources, thereby enabling the feasibility of multi-bit data storage within a single MTJ. Through systematic investigation of the resistance–voltage characteristics of perpendicular-anisotropy MTJs with varying diameters, we found that the number of resistance states can be effectively controlled by manipulating the MTJ diameter under field-free switching conditions. In a 590 nm-diameter device, we observed up to six stable and clearly distinguishable resistance states. Based on a model of the multidomain structure in the free layer, we provide a comprehensive analysis of the sequential domain switching process and, for the first time, demonstrate the exceptional thermal stability and a 1 h retention time of these multistates over a wide temperature range (5.4–360 K). All intermediate states exhibit significant margins in both resistance values and switching voltage windows, ensuring robust error tolerance for read/write operations across wide temperature ranges. This work offers crucial experimental validation for the development of high-density multistate magnetic random access memory.