SPINTRONICS LAB: Decoupling of Spin-Orbit Torque Components in Py/W Bilayers unveiled through variation of W-resistivity
Harmonic Hall measurements were performed on a series of ferromagnetic metal/heavy metal (FM/HM) bilayers consisting of Permalloy as the FM and beta-Tungsten as the HM, and the efficiencies of the two orthogonal components of the spin-orbit torque were extracted. Two sets of Hall bar-shaped devices, differing in the aspect ratio of the voltage pickup line width and the current channel width, were studied. Within each set, the resistivity of the Tungsten layer was systematically varied over a wide range (approximately 150–1000 micro.Ohm.cm). To account for geometry-induced variations in current distribution, numerical simulations were performed, and a correction protocol was developed to normalize the torque efficiencies obtained from the conventional analysis. After applying the correction, the Slonczewski-like (anti-damping, in-plane) torque efficiency exhibited a consistent dependence on Tungsten resistivity across both device sets. In contrast, the field-like (out-of-plane) torque efficiency remained largely independent of Tungsten resistivity, reinforcing the notion of its interfacial origin.
Publication Details: Applied Physics Letters 127, 262404 (2025) , Abu Bakkar Miah, Harekrishna Bhunia, Dhananjaya Mahapatra, Soumik Aon, Partha Mitra
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Posted on: January 3rd, 2026