Large perpendicular magnetic anisotropy and tunneling magnetoresistance in thermally stable Mo/FeNiB/MgO magnetic tunnel junctions

Abstract

Ferromagnetic metal/oxide heterostructures with tunable perpendicular magnetic anisotropy (PMA) and large tunnel magnetoresistance (TMR) are building blocks of spintronic devices. With unprecedented high performance, the perpendicularly magnetized CoFeB/MgO system has been extensively investigated. Here, we report that Mo/FeNiB/MgO and its inverted structure MgO/FeNiB/Mo show large interfacial PMA with high thermal stability, it ensures spontaneous perpendicular magnetization with effective PMA field of about 5 kOe in Mo/FeNiB(1.2 nm)/MgO and MgO/FeNiB(1.5 nm)/Mo after annealing at 400 °C, comparable to the CoFeB/MgO system. Remarkably, the coercivity of perpendicularly magnetized FeNiB layers in either continuous film or patterned structure of micrometers is smaller than that of the CoFeB counterpart by an order. We have fabricated perpendicular magnetic tunnel junctions with pseudo-spin valve structure Mo/FeNiB/MgO/CoFeB/Mo, which show TMR of 113% at room temperature and 221% at 5K. These results suggest that Mo/FeNiB/MgO heterostructure can be an important PMA material candidate in exploiting next-generation spintronic devices.