New publication! – Neal Reynolds, Priyamvada Jadaun, John T. Heron, Colin L. Jermain, Jonathan Gibbons, Robyn Collette, R. A. Buhrman, Darrell G. Schlom and D. C. Ralph, “Spin-Hall Torques Generated by Rare-Earth (Lanthanide) Thin Films” Phys. Rev. B. 95, 064412 (2017).
We report an initial experimental survey of spin Hall torques generated by the rare-earth metals Gd, Dy, Ho, and Lu, along with comparisons to first-principles calculations of their spin Hall conductivities. Using spin torque ferromagnetic resonance (ST-FMR) measurements and dc-biased ST-FMR, we estimate lower bounds for the spin Hall torque ratio, ξSH, of ≈0.04 for Gd, ≈0.05 for Dy, ≈0.14 for Ho, and ≈0.014 for Lu. The variations among these elements are qualitatively consistent with results from first principles [density-functional theory (DFT) in the local density approximation with a Hubbard-U correction]. The DFT calculations indicate that the spin Hall conductivity is enhanced by the presence of the partially filled f orbitals in Dy and Ho, which suggests a strategy to further strengthen the contribution of the f orbitals to the spin Hall effect by shifting the electron chemical potential.