Here, we demonstrate numerically that shape anisotropy in MgO-based spin-torque nano-oscillators consisting of an out-of-plane magnetized free layer and an in-plane polarizer is necessary to stabilize out-of-plane magnetization precession without the need of external magnetic fields. As the in-plane anisotropy is increased, a gradual tilting of the magnetization towards the in-plane easy direction is introduced, favouring zero-field dynamics over static in-plane states. Above a critical value, zero-field dynamics are no longer observed. The optimum ratio of in-plane shape to out-of-plane uniaxial anisotropy, for which large angle out-of-plane zero-field dynamics occur within the widest current range, is reported.
Zero-field dynamics stabilized by in-plane shape anisotropy in MgO-based spin-torque oscillators
E. Kowalska, A. Kákay, C. Fowley, V. Sluka, J. Lindner, J. Fassbender, A. M. Deac; Zero-field dynamics stabilized by in-plane shape anisotropy in MgO-based spin-torque oscillators. J. Appl. Phys. 28 February 2019; 125 (8): 083902. https://doi.org/10.1063/1.5081036
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