Spatial Mapping of Torques within a Spin Hall Nano-oscillator

Abstract

Time-resolved scanning Kerr microscopy (TRSKM) was used to study precessional magnetization dynamics induced by a radio frequency (RF) current within a Al${}_2$O${}_3$/Py(5 nm)/Pt(6 nm)/Au(150 nm) spin Hall nano-oscillator structure. The Au layer was formed into two needle-shaped electrical contacts that concentrated the current in the centre of a Py/Pt mesa of 4 $\mu$m diameter. Due to the spin Hall effect, current within the Pt layer drives a spin current into the Py layer, exerting a spin transfer torque (STT). By injecting RF current, and exploiting the phase-sensitivity of TRSKM and the symmetry of the device structure, the STT and Oersted field torques have been separated and spatially mapped. The STT and torque due to the in-plane Oersted field are observed to exhibit minima at the device centre that is ascribed to spreading of RF current that is not observed for DC current. Torques associated with the RF current may destabilise the position of the self-localised bullet mode excited by the DC current, and inhibit injection locking. The present study demonstrates the need to characterise both DC and RF current distributions carefully.

References in corpus (10)

• Spin Hall effect
• Current-driven dynamics of chiral ferromagnetic domain walls
• Spin Torque Ferromagnetic Resonance Induced by the Spin Hall Effect
• Measurement of the Spin-Transfer-Torque Vector in Magnetic Tunnel Junctions
• Spectral Characteristics of the Microwave Emission by the Spin Hall Nano-Oscillator
• Electronic control of the spin-wave damping in a magnetic insulator
• On the origin of magnetization auto-oscillations in constriction-based spin Hall nano-oscillators
• CMOS compatible W/CoFeB/MgO spin Hall nano-oscillators with wide frequency tunability
• Spin-orbit torque opposing the Oersted torque in ultrathin Co/Pt bilayers
• Time resolved imaging of the non-linear bullet mode within an injection-locked nano-contact spin Hall nano-oscillator

Cited by in corpus (10)

• Roadmap of spin-orbit torques
• Fabrication of voltage gated spin Hall nano-oscillators
• Energy-efficient W${}_{\text{100-x}}$Ta${}_{\text{x}}$/CoFeB/MgO spin Hall nano-oscillators
• Combined frequency and time domain measurements on injection-locked, constriction-based spin Hall nano-oscillators
• Simultaneous Optical and Electrical Spin-Torque Magnetometry with Stroboscopic Detection of Spin-Precession Phase
• Dimensional crossover in spin Hall oscillators
• Controlling selection rules for magnon scattering in nanomagnets by spatial symmetry breaking
• A Spin Hall Ising Machine
• Spin orbit torque nano-oscillators by dipole field-localized spin wave modes
• Large Amplitude Spin-Hall Oscillations due to Field-like Torque