Pd Layer Thickness Dependence of Tunnel Magnetoresistance Properties in CoFeB/MgO-Based Magnetic Tunnel Junctions with Perpendicular Anisotropy CoFe/Pd Multilayers

The authors investigated tunnel magnetoresistance (TMR) properties in [CoFe/Pd]-multilayer/CoFeB/MgO/CoFeB/[Pd/CoFe]-multilayer magnetic tunnel junctions (MTJs) having two different Pd layer thicknesses. By reducing the Pd layer thickness from 1.2 to 0.2 nm, the TMR ratio was enhanced from 7 to 101% at the annealing temperature (T-a) of 300 degrees C. The thin Pd layers resulted in high residual B concentration in the CoFeB layer after high-T-a annealing and in the suppression of crystallization of the CoFeB layer from the fcc(111)-Pd layer side. (C) 2011 The Japan Society of Applied Physics