Figure 1: MO probe of SOFs.
(a) Schematic of the current-induced magnetization dynamics by SOFs, which is directly investigated for both metallic and insulating magnetic structures through the interaction of light with the magnetic order. The direction of applied and SOFs are shown by black arrows. Ha, HFL and HAL represent applied, field-like and anti-damping-like fields, respectively. Owing to spin–orbit interaction in heavy metal, a lateral current j produces a spin current js which propagates in perpendicular direction. (b) The optical microscope image of the central region of the device in which the laser (white spot) is tightly focused near the centre of the device. The laser spot size is measured at ∼1 μm, which is much smaller than the dimensions of the device, implying the imaging capabilities of the optical probe. (c) Schematic of the experimental set-up depicting the IP current and magnetic field and the backscattering geometry of the probe laser beam. A linearly polarized light is focused on the device using a microscope objective. The intensity of the light is modulated by a photoelastic modulator at 100 kHz. The polarization of the reflected beam is analysed using a half-wave plate at 45°, Wollaston prism and balanced photodiode. Two successive lock-in amplifiers are used to measure the Kerr rotation θK and the modulated Kerr signal ΔθK induced by an IP a.c. current j with frequency of ∼277 Hz while the external magnetic field is IP.
