Abstract:
The generation, detection, and manipulation of pure spin current utilizing spin-orbit coupling in spin Hall materials, including non-magnetic heavy metals, ferromagnets, and antiferromagnets, are attracting much attention. I will discuss in this talk three aspects where heavy metals and 3d magnets play the major roles. (1) The anisotropic spin-to-charge conversion in Bismuth (Bi). Bi, being the heaviest nonradioactive element in the Periodic Table, is an important and intriguing element for quantum materials. We show that the hexagonal crystal structure of Bi profoundly modifies the spin-to-charge conversion anisotropically. (2) The enhancement of the spin to charge conversion through spin fluctuation. It is widely accepted that spin Hall angle qSH, which measures the prowess to generate pure spin current, is intrinsic to the material. We show that the spin current and the value of qSH can be greatly enhanced beyond their intrinsic limit by exploiting spin fluctuations in 3d magnets, including spin-glass CuMn alloys and ferromagnetic CuNi alloys. (3) Detection and manipulation of antiferromagnetic Néel vectors. We report that, contrary to many prior claims, there is no evidence of spin current-induced spin-orbit torque switching in the antiferromagnetic insulator NiO. We have also unambiguously demonstrated the detection and manipulation of the Néel vector in the uniaxial antiferromagnet Cr2O3 through spin current. These studies broaden our understanding of pure spin current in heavy metals and 3d magnets and would offer significant advantages in developing electrically controlled energy-efficient spintronic.