Thermal stability for domain wall mediated magnetization reversal in perpendicular STT MRAM cells with W insertion layers
Abstract
We present an analytical model for calculating energy barrier for the magnetic field-driven domain wall-mediated magnetization reversal of a magneto-resistive random access memory (MRAM) cell and apply it to study thermal stability factor for various thicknesses of W layers inserted into the free layer (FL) as a function of the cell size and temperature. We find that, by increasing W thickness, the effective perpendicular magnetic anisotropy (PMA) energy density of the FL film monotonically increases, but at the same time, of the cell mainly decreases. Our analysis shows that, in addition to saturation magnetization Ms and exchange stiffness constant Aex of the FL film, the parameter that quantifies the of the cell is its coercive field Hc, rather than the net PMA field Hk of the FL film comprising the cell.