Regensburg 2019 – scientific programme
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MA: Fachverband Magnetismus
MA 38: Spin hall effects
MA 38.5: Talk
Wednesday, April 3, 2019, 18:15–18:30, H52
Ultra-low switching current density in all-amorphous W-Hf/CoFeB/TaOx films — •Katharina Fritz and Markus Meinert — Center for Spinelectronic Materials and Devices, Physics Department, Bielefeld University, Germany
In our previous work [1], we investigated the spin Hall effect of W-Hf thin films, which exhibit a phase transition from a segregated phase mixture to an amorphous alloy below 70% W. Accompanied by a jump in
resistivity, the spin Hall angle shows a pronounced maximum at the composition of the phase transition. A maximum spin Hall angle of θSH=0.20 was obtained for amorphous W0.7Hf0.3. Due to their amorphous character, the films are expected to contain few pinning centers and, therefore, to show fast domain wall motion, making them interesting in the context of current induced SOT switching.
Using Kerr microscopy, we study the domain wall structure and magnetization switching of amorphous W-Hf/CoFeB/TaOx stacks with perpendicular magnetic anisotropy and large spin Hall angle. We observe current induced domain wall motion without an in-plane assist field, indicating Néel-type domain walls. Investigations of magnetization switching as a function of in-plane assist-field and
current pulse-widths reveal switching current densities as low as 3× 109 A/m2 in the dc limit.
[1] K. Fritz, S. Wimmer, H. Ebert, and M. Meinert, Phys. Rev. B 98,
094433 (2018)