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technical paper
Blanket Film Spin Orbit Torque Characterization via Four Probe Measurement
Spin-orbit torque characterization techniques generally require Hall cross that generally demands lithography resources and time. As the interest in exploring materials for improved SOT performance surges, an efficient technique to characterize SOT efficiencies with minimal processes, equipment, and time is highly desirable. Here, we demonstrate a lithography-free technique to determine the spin-orbit torque efficiency in perpendicular magnetic anisotropy ferromagnetic heterostructure. By utilizing a customized fzour-point probe in a rhombus geometry, harmonic Hall measurement was performed on a blanket films of Pt/Co/Ti structure to characterize the spin-orbit torque efficiency. Due to the non-uniform current distribution across the blanket film, a correction factor is experimentally evaluated using the ratio of the damping-like field measured on the blanket film to that of a fabricated Hall device with identical material heterostructure. Additionally, this correction factor is analytically derived and experimentally shown to be determined by the configuration of the probes and is independent of the structure material. Our measurement reveals that by performing a single calibration process for the particular set of probes, the same correction factor was validated on a second ferromagnetic heterostructure, Ti/Pt/Co/Ta hence it can be applied to other SOT films stack measurements. Our four-probe harmonic Hall technique provides an alternative and swift way for SOT investigations by eliminating multiple lithography processes necessary in conventional approaches.