Spin Transfer Switching and Interlayer Coupling in CPP-GMR Structures with GdFeCo Free Layer

Abstract

The spin transfer switching in the TbCoFe / CoFeB / Cu / GdFeCo current perpendicular to plane (CPP) giant magnetoresistance (GMR) structures were studied. The GMR junction exhibited 0.1 % MR ratio, and current induced magnetization switching of the GdFeCo free layer was confirmed by a 100 msec pulse current. The difference of the critical current density between Jc+ (anti-parallel (AP) to parallel (P)) and Jc- (P to AP) was estimated to be 15.3 × 107 A/cm2, and thus the average current density to be 7.7 × 107 A/cm2. It was confirmed that the sign of the interlayer coupling between GdFeCo and TbCoFe / CoFeB depended on the relative direction of the transition metal (TM) - moments of GdFeCo free layer and TbCoFe / CoFeB pin layer, which means the coupling is dominated by the exchange coupling through Cu spacer.