Current induced magnetization switching of perpendicularly magnetized CoFeB layer by spin orbit torque

Abstract

This master dissertation describes an experimental study on current induced magnetization switching induced by spin orbit torque in W/CoFeB/MgO stack with changing annealing temperature. In the first place, we investigate magnetic property of W/CoFeB/MgO stack with changing annealing temperature. As annealing temperature increases, in-plane anisotropy field increase but saturation magnetization decreases. Two property can effect current switching because large in-plane anisotropy and saturation magnetization make switching magnetization hard. Secondly, magnetization switching that occur while injecting current into W/CoFeB/MgO stack was investigated. Current level reached at certain critical current value, emerging magnetization reversal was confirmed. Also, changing critical current density value with annealing temperature was figured out. Thirdly, changing effective field induced by spin orbit torque was confirmed with increasing current using numerical fitting method. Effective field value is derived based on AC first and seco nd harmonic measurement and calculated numerical fitting method. Also, it is confirmed that effective field induced by spin orbit torque was proportional to current. Lastly, relation with current density and effective field induced by spin orbit torque was investigated with changing annealing temperature. As the annealing temperature increased, effective field value increasing was confirmed. With this result, critical current density changing with annealing temperature was investigated. By excluding anisotropic field influence, critical current density decreasing with annealing temperature increasing is confirmed because of effective field increasing with annealing temperature.