Spin Hall magnetoresistance in 2D PtSe₂/ferromagnet heterostructures

The recent discovery of inherently stable two-dimensional (2D) transition-metal dichalcogenides (TMDs) provides a unique platform for spintronic devices. However, its efficacy for electric detection by spin Hall magnetoresistance (SMR) has not been established yet. In this work, we report on SMR in 2D TMDs/ferromagnet heterostructures, i.e., PtSe2/NiFe (Py), whose magnitude reaches the maximum with bilayer PtSe2. Notably, the SMR value in bilayer PtSe2/Py heterostructures undergoes a sign change with increasing Py thickness. For thinner Py samples, the SMR rapidly decreases with increasing Py thickness, eventually changing from positive to negative. In the case of intermediate Py thicknesses, the SMR consistently exhibits negative behavior. However, for thicker Py samples, the negative SMR values gradually decrease. This complex behavior is attributed to the dominant and competing mechanisms that contribute to SMR, including the spin Hall effect (or Rashba-induced effect) and its inverse effect, the orbital Hall effect and its inverse effect, as well as interfacial spin-orbit-coupling-induced spin-current-to-charge-current conversion. These findings would expand the arsenal for advanced spintronic applications based on 2D TMDs.