Atomic and electronic structure of the CoFeB∕MgO interface from first principles

Abstract

First-principles calculations of the atomic and electronic structure of crystalline CoFeB∕MgO∕CoFeB magnetic tunnel junctions (MTJs) are performed to understand the effect of B on spin-dependent transport in these junctions. The authors find that it is energetically favorable for B atoms to reside at the crystalline CoFeB∕MgO interface rather than remain in the bulk of the crystalline CoFeB electrode. The presence of B at the interfaces is detrimental to tunneling magnetoresistance (TMR) because it significantly suppresses the majority-channel conductance through states of Δ1 symmetry. Preventing B segregation to the interfaces during annealing should result in an enhanced TMR in CoFeB∕MgO∕CoFeB MTJs.