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Understanding the mechanisms of unidirectional magnetoresistance (UMR) has become an important topic for its potential application of a two-terminal spin-orbit torque device. Field sweep DC measurements have been proposed and adopted to measure the value of UMR instead of second harmonic measurements. In this paper, potential measurement errors in conventional DC measurements are investigated. Oersted field and field-like torque usually do not influence the measurement, but a large field-like torque was found to lead to an anisotropic magnetoresistance difference when the sample is not perfectly aligned with the external field. The existence of ordinary magnetoresistance was also found to contribute to a large background. In this paper, an alternative measurement method for UMR was proposed and demonstrated to address those issues related to previous DC measurements. Our work may broaden the understanding of the error sources of UMR measurements and provide a reliable DC measurement method for the characterization of UMR.
Bibliographical noteFunding Information:
This work was supported, in part, by SMART, one of the seven centers of nCORE, a Semiconductor Research Corporation Program, sponsored by the National Institute of Standards and Technology (NIST) and by the UMN MRSEC Program under Award No. DMR-2011401. This work utilized the College of Science and Engineering (CSE) Characterization Facility at the University of Minnesota (UMN) supported, in part, by the NSF through the UMN MRSEC program. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under Award No. ECCS-2025124. J.-P.W. also acknowledges support from Robert Hartmann Endowed Chair Professorship.
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