Optimization of Tunneling Magnetoresistance in Perpendicular Magnetic Tunnel Junctions With Co|Pd Reference Layers

We report on the optimization of Co|Pd-multilayer-based reference layers in magnetic tunnel junctions with perpendicular magnetic anisotropy. By inserting a thin Ta-spacer layer between the CoFeB interfacial layer and Co|Pd multilayer, a high tunneling magnetoresistance up to 98.5% can be achieved. Electron energy loss spectroscopy and synchrotron X-ray diffraction studies show that the high magnetoresistance is related primarily to the suppression of Pd diffusion and secondarily to improved CoFeB texture during annealing.