13:00 〜 13:15
▲ [11p-Z08-3] Study on the dynamic magnetic properties in Ta-O/Co-Fe-B stacks with different interface condition
キーワード：Temperature dependence of Magnetization dynamics, surface oxidized TaOx/CoFeB, Broadband ferromagnetic resonance measurement
The spin-orbit torque induced switching in oxide/ferromagnetic stacks has attracted much attention as a new method for spintronic device applications since the switching in these stacks showed a high efficiency by tuning the surface oxidization. Since the high efficiency closely correlates to both of the dynamic magnetic properties and the interface condition in these stacks, a detailed understanding of their correlation is important from the scientific points of view. Herein we selected Ta-O/Co-Fe-B stacks, and studied the change in the dynamic magnetic properties by controlling the interface condition.
Ta-O (1 nm)/Co-Fe-B (1.3 nm)/MgO (1.3 nm)/Ta (1 nm) stacks were fabricated the RF sputtering. Ta-O layers were formed by naturally oxidizing thin Ta layers at the different oxygen pressure (P). The post-annealing process was conducted at a temperature (T_an) ranging from 523 K to 673 K in a vacuum to control the interfacial anisotropy (K_s). As for their dynamic magnetic properties, the effective saturation magnetization (4pi_M_s, eff) and the damping constant (a) were estimated using a broadband FMR measurement.
Figure 1 shows the change in 4pi_M_s, eff and (a) with T_an for the stacks oxidized at different P. For all stacks, as T_an increases, 4pi_M_s, eff slightly decreases while (a) increases. At all T_an except 673 K, (a) values at P above 0.1 Pa are lower than that at P of 0.03 Pa. Furthermore, to get more insight, K_s was estimated by K_s = (4pi_M_s, eff - 4pi_M_s)x(t_Co-Fe-B x 4pi_M_s/2), where t_Co-Fe-B is the Co-Fe-B layer thickness, and 4pi_M_s is the saturation magnetization, and then was summarized in Fig. 1 (c) as a function of T_an. The values at P above 0.1 Pa become lower than that at P = 0.03 Pa, meaning that (a) and K_s are correlated with each other in the surface oxidized stacks. These results suggested that the surface oxidization plays an important role in controlling (a) in these stacks.<br
Ta-O (1 nm)/Co-Fe-B (1.3 nm)/MgO (1.3 nm)/Ta (1 nm) stacks were fabricated the RF sputtering. Ta-O layers were formed by naturally oxidizing thin Ta layers at the different oxygen pressure (P). The post-annealing process was conducted at a temperature (T_an) ranging from 523 K to 673 K in a vacuum to control the interfacial anisotropy (K_s). As for their dynamic magnetic properties, the effective saturation magnetization (4pi_M_s, eff) and the damping constant (a) were estimated using a broadband FMR measurement.
Figure 1 shows the change in 4pi_M_s, eff and (a) with T_an for the stacks oxidized at different P. For all stacks, as T_an increases, 4pi_M_s, eff slightly decreases while (a) increases. At all T_an except 673 K, (a) values at P above 0.1 Pa are lower than that at P of 0.03 Pa. Furthermore, to get more insight, K_s was estimated by K_s = (4pi_M_s, eff - 4pi_M_s)x(t_Co-Fe-B x 4pi_M_s/2), where t_Co-Fe-B is the Co-Fe-B layer thickness, and 4pi_M_s is the saturation magnetization, and then was summarized in Fig. 1 (c) as a function of T_an. The values at P above 0.1 Pa become lower than that at P = 0.03 Pa, meaning that (a) and K_s are correlated with each other in the surface oxidized stacks. These results suggested that the surface oxidization plays an important role in controlling (a) in these stacks.<br