A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction

Magnetic tunnel junctions (MTJS) with ferromagnetic electrodes possessing a perpendicular magnetic easy axis are of great interest as they have a potential for realizing next-generation hight-density non-volatile memory and logic chips with high thermal stability and low critical current for current-induced magnetization switching(1-3). To attain perpendicular anisotropy, a number of material system have been explored as electrodes, which include rare-earth/transition-metal alloys(4,5), L1(0)-ordered (Co, Fe)-Pt alloys(3,6,7) and Co/(Pd, Pt) multilayers(1,8-10). However, none of them so far satisfy high thermal stability at reduced dimension, low-current current-induced magnetization switching and high tunnel magnetoresistance ratio all at the same time. Here, we use interfacial perpendicular anisotropy between the ferro-magnetic electrodes and the tunnel barrier of the MTJ by employing the material combination of CoFeB-MgO, a system widely adopted to produce a giant tunnel magnetoresistance ratio in MTJs with in-plane anisotropy(11-13). This approach requires no material other than those used in conventional in-plane-anisotropy MTJs. The perpendicular MTJs consisting of Ta/CoFeB/MgO/CoFeB/Ta show a high tunnel magnetoresistance ratio, over 120%, high thermal stability at dimension as low as 40 nm diameter and a low switching current of 49 mu A.