Voltage-Controlled Magnetic Anisotropy in Tb–Fe–Co/MgO/Gd–Fe MTJ Devices

Voltage-controlled magnetic anisotropy (VCMA) effect of a relatively thick Co-Fe (X nm)/Gd (Y nm)/Gd-Fe (9 nm) free layers in Tb-Fe-Co/MgO/Gd-Fe magnetic tunnel junctions was investigated. We have observed the clear magnetic anisotropy change from in-plane to out-of-plane in the Co-Fe (0.3 nm)/Gd (0.2 nm)/Gd-Fe (9 nm) free layer by applying a dc voltage of +1.4 V to the free layer. The evaluated magnetic anisotropy energy change with electric field of the Co-Fe (0.3 nm)/Gd (0.1 nm)/Gd-Fe(9 nm) free layer was 19 fJ/Vm, which was comparable with the reported value. The successful VCMA for thick magnetic materials was attributed to the perpendicular magnetic anisotropy design of the free layer that is strongly influenced by the VCMA change of the thin insertion Co-Fe layer.