Strong anti-strain capacity of CoFeB/MgO interface on electronic structure and state coupling**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0400801), the National Natural Science Foundation of China (Grant Nos. 61774128, 61674124, 11604275, 11304257, and 61227009), the Natural Science Foundation of Fujian Province of China (Grant Nos. 2017J01012, 2014J01026, 2016J01037, and 2015J01028), and the Fundamental

Abstract

Electronic structure and spin-related state coupling at ferromagnetic material (FM)/MgO (FM = Fe, CoFe, CoFeB) interfaces under biaxial strain are evaluated using the first-principles calculations. The CoFeB/MgO interface, which is superior to the Fe/MgO and CoFe/MgO interfaces, can markedly maintain stable and effective coupling channels for majority-spin state under large biaxial strain. Bonding interactions between Fe, Co, and B atoms and the electron transfer between Bloch states are responsible for the redistribution of the majority-spin state, directly influencing the coupling effect for the strained interfaces. Layer-projected wave function of the majority-spin state suggests slower decay rate and more stable transport property in the CoFeB/MgO interface, which is expected to maintain a higher tunneling magnetoresistance (TMR) value under large biaxial strain. This work reveals the internal mechanism for the state coupling at strained FM/MgO interfaces. This study may provide some references to the design and manufacturing of magnetic tunnel junctions with high tunneling magnetoresistance effect.