Perpendicular magnetic tunnel junctions with synthetic ferrimagnetic pinned layer

Abstract

We have fabricated perpendicular magnetic tunnel junctions (p-MTJs) consisting of CoPt/Ru/CoFeB/MgO/CoFeB/Pt. The tunnel magnetoresistance (TMR) of the p-MTJs characterizes the magnetic configurations of the CoPt/Ru/CoFeB pinned layer. The magnetic moment of the CoFeB, which is naturally in-plane, can be aligned to the out-of-plane direction by an indirect exchange coupling with the hcp CoPt alloy having large perpendicular magnetic anisotropy. When the applied field is relatively smaller than the exchange coupling strength, the p-MTJs show a configurationally negative TMR as a consequence of an antiparallel alignment of the CoPt and CoFeB magnetic moments. c 2010 American Institute of Physics. [doi: 10.1063/1.3486059]