Effects of annealing on coercivity, switching mechanisms, and structural characteristics of Co/Pd multilayer for magnetic memory

Abstract

This study investigates the effects of annealing on the magnetic and structural properties of Co/Pd multilayers, which are promising candidates for perpendicular magnetic tunnel junctions, critical to magneto-resistive random-access memory (MRAM) applications. Co/Pd multilayers with various bilayer counts (5, 10, 15, and 20) were synthesized via DC magnetron sputtering and subjected to annealing at temperatures ranging from 250 to 450 °C. Magnetic measurements, including standard magnetization-vs-field major hysteresis loops and first-order reversal curve analysis, showed that annealing increased coercivity, reaching a maximum of 5100 Oe at 450 °C for 20 bilayers. Magneto-Optical Kerr Effect imaging confirmed domain-wall motion as the switching mechanism, except in the highest temperature annealed samples, which appear to behave more like independent particles. Structural characterization using x-ray diffraction revealed enhanced crystallinity with annealing, indicating improved atomic ordering. Atomic force microscopy demonstrated increased surface roughness with bilayer count due to increased thickness. These results show that Co/Pd-based multilayers are tolerant of high-temperature processing, as required for CMOS-based MRAM.