Giant Perpendicular Magnetic Anisotropy in Mo-Based Double-Interface Free Layer Structure for Advanced Magnetic Tunnel Junctions

A strong perpendicular magnetic anisotropy (PMA) and a high thermal stability are essential for long-term stable storage of data in PMA-based magnetic tunnel junctions (p-MTJs). This work investigates the magnetic anisotropy of the MgO/CoFeB/X/CoFeB/MgO double-interface free layer stacks, where X represents the spacer material. After annealing at 350 degrees C for an hour, interfacial magnetic anisotropy (K-i) as high as 4.06 mJ m(-2)is obtained in the MgO/CoFeB/Mo (0.4 nm)/CoFeB/MgO stacks, much higher than those for Ta- and W-based films. Experimental and first-principle calculation results demonstrate that bulk PMA plays a great role in the Mo-based structure, which is often negligible in Ta- and W-based structures. Moreover, a strong PMA is achieved after annealing at 500 degrees C, which is attributed to the weak interdiffusion and good uniformity as shown in high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy results. These findings help to understand the origin of strong PMA in Mo-based structures and show the promising prospect of using this structure for high-packing-density p-MTJs and other spintronic device applications down to 10 nm scale.