14:45 〜 15:00
▲ [17p-Z19-7] Investigation of spin-orbit torque induced magnetization switching in Ta-O/Co-Fe-B heterostructures
キーワード：Spin-orbit torque induced magnetization switching, surface oxidized Ta-O/Co-Fe-B, effective SOT fields
Spin-orbit torque (SOT) induced magnetization switching in oxide/ferromagnetic heterostructures has attracted immense interest owing to its potential for the development of high-performance spintronics devices, realized by tuning the surface oxidization [1]. Since both of the Slonczewski-like (H_SL) and the field-like (H_FL) effective fields would contribute to the magnetization reversal, a detailed understanding and manipulation of H_SL and H_FL in these structures are important. Herein we selected typical Ta-O/Co-Fe-B heterostructures, and studied the change in H_SL and H_FL by controlling the thickness of Ta-O layer.
From the thermally oxidized Si substrate’s side, Ta-O (t nm)/CoFeB (1.2 nm)/MgO (1.3 nm)/Ta (1.0 nm) stacks with various values of Ta-O layer’s thickness (t) were fabricated by DC/RF sputtering. Ta-O layer was formed by naturally oxidizing Ta layer at 0.3 Pa. The effective fields, H_SL and H_FL were evaluated using an extended harmonic Hall measurement for Hall bar devices.
The sign and absolute values (|H_SL(FL)|) of the effective fields are consistent with those in the previous work on Ta/Co-Fe-B/MgO stacks [2]. Figure 1 shows t dependence of |m0H_SL(FL)|/I, where I is the total current applying to the device (a), and H_FL/H_SL in comparison with that of a non-oxidized stack (b). Both of |m0H_SL|/I and |m0H_FL|/I increase and converge to a certain value as t increases, suggesting a bulk effect, such as the spin Hall effect, as an origin of SOT. On the other hand, |H_FL| is larger than |H_SL| and their ratio increases with t, as shown in Fig. 1 (b), suggesting an interfacial contribution such as the Rashba-Edelstein effect (REE), if one assumes that H_FL originates from REE [3]. These results are of importance to understand the SOT induced magnetization switching, and to design spintronic devices using oxidized HM/FM systems. [1] Nat. Commun. 7, 13069, 2016. [2] Appl. Phys. Lett. 103, 262407, 2013. [3] Phys. Rev. Appl. 13, 054014, 2020.
From the thermally oxidized Si substrate’s side, Ta-O (t nm)/CoFeB (1.2 nm)/MgO (1.3 nm)/Ta (1.0 nm) stacks with various values of Ta-O layer’s thickness (t) were fabricated by DC/RF sputtering. Ta-O layer was formed by naturally oxidizing Ta layer at 0.3 Pa. The effective fields, H_SL and H_FL were evaluated using an extended harmonic Hall measurement for Hall bar devices.
The sign and absolute values (|H_SL(FL)|) of the effective fields are consistent with those in the previous work on Ta/Co-Fe-B/MgO stacks [2]. Figure 1 shows t dependence of |m0H_SL(FL)|/I, where I is the total current applying to the device (a), and H_FL/H_SL in comparison with that of a non-oxidized stack (b). Both of |m0H_SL|/I and |m0H_FL|/I increase and converge to a certain value as t increases, suggesting a bulk effect, such as the spin Hall effect, as an origin of SOT. On the other hand, |H_FL| is larger than |H_SL| and their ratio increases with t, as shown in Fig. 1 (b), suggesting an interfacial contribution such as the Rashba-Edelstein effect (REE), if one assumes that H_FL originates from REE [3]. These results are of importance to understand the SOT induced magnetization switching, and to design spintronic devices using oxidized HM/FM systems. [1] Nat. Commun. 7, 13069, 2016. [2] Appl. Phys. Lett. 103, 262407, 2013. [3] Phys. Rev. Appl. 13, 054014, 2020.