MgO-based magnetic tunnel junctions and their applications

Abstract

Massive research has been carried out on magnetic tunnel junctions (MTJs), which consist of two ferromagnetic layers sandwiched by a thin insulating barrier, since they were first discovered in 1970. The electrode resistance of these multilayer structures is usually low when the magnetization directions of the two ferromagnetic layers are in a parallel configuration and high when they are antiparallel. The resistance change following the field switch makes MTJs perfect candidates for magnetic field sensors and for the storage elements in memory devices. The recent breakthrough for MTJs happened in 2004 when highly oriented (001) MgO thin films were used as the tunnel barrier. Compared to conventional AlOx and TaOx barriers MgO-based MTJs show a huge tunnel magnetoresistance (TMR) and relatively lower resistance and area products which make them more promising as magnetic random access memory (MRAM ) elements and low field sensors.