The 81st JSAP Autumn Meeting, 2020

Presentation information

Oral presentation

10 Spintronics and Magnetics » 10.1 Emerging materials in spintronics and magnetics (including fabrication and charactrization methodologies)

[11p-Z08-1~19] 10.1 Emerging materials in spintronics and magnetics (including fabrication and charactrization methodologies)

Fri. Sep 11, 2020 12:30 PM - 5:45 PM Z08

Takahide Kubota(Tohoku Univ.), Koyama Tomohiro(阪大), Masuda Keisuke(物材機構)

1:00 PM - 1:15 PM

[11p-Z08-3] Study on the dynamic magnetic properties in Ta-O/Co-Fe-B stacks with different interface condition

Anh ThiVan Nguyen1,2,3, Shunsuke Fukami1,2,3,4, Yoshiaki Saito3, Shuichiro Hashi4, Shoji Ikeda1,2,3, Tetsuo Endoh1,2,3,4,5, Yasushi Endo1,2,5 (1.CSIS, Tohoku Univ., 2.CSRN, Tohoku Univ., 3.CIES, Tohoku Univ., 4.RIEC, Tohoku Univ., 5.ECEI, Tohoku Univ.)

Keywords: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