All electrical manipulation of magnetization dynamics in a ferromagnet by antiferromagnets with anisotropic spin Hall effects

We investigate spin-orbit torques of metallic CuAu-I-type antiferromagnets using spin-torque ferromagnetic resonance tuned by a dc-bias current. The observed spin torques predominantly arise from diffusive transport of spin current generated by the spin Hall effect. We find a growth-orientation dependence of the spin torques by studying epitaxial samples, which may be correlated to the anisotropy of the spin Hall effect. The observed anisotropy is consistent with first-principles calculations on the intrinsic spin Hall effect. Our work demonstrates large tunable spin-orbit effects in magnetically-ordered materials.Comment: 7 pages, 6 figures, to appear in Phys. Rev. B (2015

Fractal Conductance Fluctuations in Gold--Nanowires

A detailed analysis of magneto-conductance fluctuations of quasiballistic gold-nanowires of various lengths is presented. We find that the variance $=$ when analyzed for $\Delta B$ much smaller than the correlation field $B_c$ varies according to $<(\Delta G)^2>\propto \Delta B^{\gamma}$ with $\gamma < 2$ indicating that the graph of $G$ vs. $B$ is fractal. We attribute this behavior to the existence of long-lived states arising from chaotic trajectories trapped close to regular classical orbits. We find that $\gamma$ decreases with increasing length of the wires.Comment: 5 pages, Revtex with epsf, 4 Postscript figures, final version accepted as Phys. Rev. Let

Spin Hall Effects in Metallic Antiferromagnets

We investigate four CuAu-I-type metallic antiferromagnets for their potential as spin current detectors using spin pumping and inverse spin Hall effect. Nontrivial spin Hall effects were observed for FeMn, PdMn, and IrMn while a much higher effect was obtained for PtMn. Using thickness-dependent measurements, we determined the spin diffusion lengths of these materials to be short, on the order of 1 nm. The estimated spin Hall angles of the four materials follow the relationship PtMn>IrMn>PdMn>FeMn, highlighting the correlation between the spin-orbit coupling of nonmagnetic species and the magnitude of the spin Hall effect in their antiferromagnetic alloys. These experiments are compared with first-principles calculations. Engineering the properties of the antiferromagnets as well as their interfaces can pave the way for manipulation of the spin dependent transport properties in antiferromagnet-based spintronics

Reduced spin-Hall effects from magnetic proximity

Harnessing spin-orbit coupling for the manipulation of spins and magnetization via electric charge currents is the key objective of spin-orbitronics. Towards this end ferromagnetic materials are combined with nonmagnetic materials with strong spin-orbit coupling (typically involving heavy elements). However, many of the nominally nonmagnetic materials are highly susceptible to magnetic proximity effects, and the role of induced moments for spin transport has been controversial. Here we demonstrate that for Pt and Pd increased induced magnetic moments are correlated with strongly reduced spin-Hall conductivities. This observation finds an intuitive explanation in the development of a spin splitting of the chemical potential and the energy dependence of the intrinsic spin-Hall effect determined by first-principles calculations. This work provides simple guidance towards the optimization of spin current efficiencies for devices based on spin-orbit coupling phenomena

Roadmap of Spin–Orbit Torques

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