Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 42: Posters Magnetism I

MA 42.45: Poster

Wednesday, March 18, 2020, 15:00–18:00, P3

Current direction dependent frequency ranges of spin Hall nano-oscillators by adding a magnetic layer — •Toni Hache^{1, 2}, Tillmann Weinhold¹, Yancheng Li¹, Jürgen Fassbender^{1, 3}, Olav Hellwig^{1, 2}, and Helmut Schultheiss^{1, 3} — ¹HZDR — ²TU Chemnitz — ³TU Dresden

Spin Hall nano-oscillators (SHNO) convert dc currents in microwave oscillations of the magnetization. The frequency can be tuned by external magnetic fields, the applied dc current or by injection locking if an additional microwave field is applied to the SHNO. Here, we demonstrate a new approach to extend the frequency range of a SHNO by adding an additional ferromagnetic layer. Moreover, the auto-oscillations can be switched from one to the other ferromagnetic layer by switching the current direction. A constriction-based SHNO consisting of a Py(5nm)/Pt(7nm)/CoFeB(5nm) layer stack with 2 nm Ta as seed and capping layer was used. If a dc current is applied to the structure, a pure spin current is generated by the spin Hall effect in the Pt layer. For a fixed current direction the spin polarization of the pure spin currents entering in the Py and CoFeB layers have opposite directions. Therefore, only one of both ferromagnetic layers experiences a decrease of damping due to the spin transfer torque and can show auto-oscillations of the magnetization. To change the frequency of the SHNO, the dc current direction has to be switched in order to switch the auto-oscillations to the other material with a different frequency range. The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft within programme SCHU 2922/1-1.