Spin transfer switching current reduction in magnetic tunnel junction based dual spin filter structures

摘要

Spin-transfer-driven magnetization switching was studied in single magnetic tunneling junctions (MTJ: Ta/PtMn/CoFe/Ru/CoFeB/Al_2O_3/CoFeB/Ta) and dual spin filters (DSF: Ta/PtMn/CoFe/Ru/CoFeB/Al_2O_3/CoFeB/spacer/CoFe/PtMn/Ta) having resistance-area (RA) product in the range of 10-30 Ω μm~2 and tunnel magnetoresistance (TMR) of 15%-30%. The intrinsic critical current density (J_(c0)) was estimated by extrapolating experimentally obtained critical current density (J_c) versus pulse width (τ) data to a pulse width of 1 ns. J_c, extrapolated to τ of 1 ns (～J_(c0)), was 7 X 10~6 and 2.2 X 10~6 A/cm~2, respectively, for the MTJ and improved DSF samples having identical free layers. Thus, a significant enhancement of the spin transfer switching efficiency is seen for DSF structures compared to the single MTJ case.