Damping parameter and interfacial perpendicular magnetic anisotropy of FeB nanopillar sandwiched between MgO barrier and cap layers in magnetic tunnel junctions

We systematically investigated the Gilbert damping (alpha) and interfacial perpendicular magnetic anisotropy (k(1)) in magnetic tunnel junctions with a MgO-barrier/FeB/MgO-cap layered structure using the spin-torque diode effect. By increasing the MgO cap thickness, alpha decreased, whereas. K-i increased monotonically. Values down to 0.0054 for a and up to 3.3 erg/cm(2) for K-1 were obtained for a MgO cap thickness of 0.6 nm. The small alpha and large K-1 suggest that MgO-capped FeB is a suitable free layer for spintronics devices such as spin-torque oscillators and spin-torque magnetic random access memories. (C) 2014 The Japan Society of Applied Physics