13:30 〜 15:30
▲ [18p-PB1-19] Voltage-controlled magnetic anisotropy of Co1-xNix ultrathin alloy at interface with MgO
キーワード：Voltage-controlled magnetic anisotropy, Co, Ni
Voltage-controlled magnetic anisotropy (VCMA) has been intensively studied for establishing ultra-low-power memory device. However, the amplitude of VCMA has to be increased significantly. In ultra-thin ferromagnetic metal, the VCMA effect arises from a charge-doping to 3d-orbital occupation of interfacial magnetic atoms by a bias-electric field [1-3]. Hence, the manipulation of 3d-orbital state of the interfacial ferromagnetic layer can be a key to obtain a high VCMA value. In this study, we focused on the difference of the number of d-orbital-electron between Co and Ni, and investigated the VCMA effect of Fe/Co1-x/Nix/MgO multilayer using spin-wave spectroscopy.
Multilayer film structure was grown onto NaCl-type single-crystal MgO(001) substrate as depicted in Fig. 1. The Co and Ni atomic layers were inserted in between Fe/MgO sandwich. By employing wedges shape, the fraction of Ni layer (x) was controlled. Then, the multilayer was pattern into rectangular shape. Two microsize antennae were grown onto it. An in-plane external magnetic field was applied to excite magneto-static surface spin-wave (MSSW). The characterization of VCMA effect was performed through vector network analyzer, by acquiring the modulation of scattering parameter (S21 and S12) with and without bias-voltage. The bias-electric-field amplitude was 8 mV/nm. Figure 2 shows the Ni fraction (x) dependence of Co1-x/Nix/MgO VCMA coefficient. x = 0 and x = 1 are represent 100%-Co and 100%-Ni, respectively. It is seen that the increase of Ni fraction (x) decrease the VCMA energy significantly. The highest VCMA of 280 fJ/Vm was obtained in Fe/Co(0.28 nm)/MgO (x = 0). In the presentation, voltage-induced iDMI change and the influence of heavy metal layer of Pd will be also discussed.
Multilayer film structure was grown onto NaCl-type single-crystal MgO(001) substrate as depicted in Fig. 1. The Co and Ni atomic layers were inserted in between Fe/MgO sandwich. By employing wedges shape, the fraction of Ni layer (x) was controlled. Then, the multilayer was pattern into rectangular shape. Two microsize antennae were grown onto it. An in-plane external magnetic field was applied to excite magneto-static surface spin-wave (MSSW). The characterization of VCMA effect was performed through vector network analyzer, by acquiring the modulation of scattering parameter (S21 and S12) with and without bias-voltage. The bias-electric-field amplitude was 8 mV/nm. Figure 2 shows the Ni fraction (x) dependence of Co1-x/Nix/MgO VCMA coefficient. x = 0 and x = 1 are represent 100%-Co and 100%-Ni, respectively. It is seen that the increase of Ni fraction (x) decrease the VCMA energy significantly. The highest VCMA of 280 fJ/Vm was obtained in Fe/Co(0.28 nm)/MgO (x = 0). In the presentation, voltage-induced iDMI change and the influence of heavy metal layer of Pd will be also discussed.