Magneto-Optical Detection of Spin-Orbit Torque Phenomena Using Sagnac Interferometer microscope

Author / Creator

MMM 2020 (2020)

Conferences

MMM 2020 E3: New Probing Techniques for Spin Torques (2020)

Available as

Online

Summary

An important aspect of spin-orbitronics is to electrically manipulate the spin degree of freedom in order to achieve spin-based logic and memory functionalities. Spin-orbit torques (SOTs), direct c...

An important aspect of spin-orbitronics is to electrically manipulate the spin degree of freedom in order to achieve spin-based logic and memory functionalities. Spin-orbit torques (SOTs), direct control of the magnetization via spin-orbit interaction of materials by passing an electric current, have been demonstrated in a variety of metallic and insulating ferromagnetic/non-magnetic heavy metal bilayers utilizing both magneto-transport and magneto-optical Kerr effect (MOKE) measurements. Whereas the conventional MOKE measurement successfully expands the detectability of SOTs, an AC current modulation in the SOT devices is required to achieve the desired sensitivity. Here, we show that instead of using the AC current modulation, the SOT-induced effect can be studied by observing static magnetization switching under a DC current excitation taking advantage of the ultrahigh sensitivity of a Sagnac interferometer microscope. Upon the DC current excitation, spatially resolved static magnetization switching in a prototypical SOT device, i.e., NiFe/Pt bilayer is directly measured, by which a current-induced Oersted field, joule-heating, and other parasite artifacts can be well-separated. Our work provides a promising continuous-wave magneto-optical approach to optically characterize the static spin Hall angle in a range of SOT devices without the need for the AC current modulation. This work was supported by NSF-ECCS under grants No. 1933301 and 1933297.

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