Energy barrier and domain wall thermal reversal in magnetic elliptic cylinders

The energy barriers are studied for an in-plane magnetized elliptic magnetoresistive random access memory cell using the nudged elastic band method with finite-element micromagnetics. Our calculations show that the transition between coherent magnetization rotation and domain wall mediated thermal reversal appears at an ellipse aspect ratio greater than 2 for widths 60-90 nm. This crossover point is almost independent of the value of the partial perpendicular magnetic anisotropy and has only a negligibly weak dependence of the width and thickness of the cell and only weakly depends on the exchange stiffness for reasonable in-plane Spin-Transfer Torque Magnetic Random Access Memory parameters. We developed an analytical model for the thermal barrier, which agrees with the numerical results.