Asymmetric Angular Dependence Of Spin-Transfer Torques In Cofe/Mg-B-O/Cofe Magnetic Tunnel Junctions

Using a first-principles noncollinear wave-function-matching method, we studied the spin-transfer torques (STTs) in CoFe/Mg-B-O/CoFe(001) magnetic tunnel junctions (MTJs), where three different types of B-doped MgO in the spacer are considered, including B atoms replacing Mg atoms (Mg3BO4), B atoms replacing O atoms (Mg3BO4), and B atoms occupying interstitial positions (Mg3BO4) in MgO. A strong asymmetric angular dependence of STT can be obtained both in ballistic CoFe/Mg3BO4 and CoFe/Mg3BO4 based MTJs, whereas a nearly symmetric STT curve is observed in the junctions based on CoFe/Mg3BO4. Furthermore, the asymmetry of the angular dependence of STT can be suppressed significantly by the disorder of B distribution. Such skewness of STTs in the CoFe/Mg-B-O/CoFe MTJs could be attributed to the interfacial resonance states induced by the B diffusion into MgO spacer. Published by AIP Publishing.