Spin-orbit torque on nuclear spins exerted by a spin accumulation via hyperfine interactions.

Spin-transfer and spin-orbit torques allow controlling magnetic degrees of freedom in various materials and devices. However, while the transfer of angular momenta between electrons has been widely studied, the contribution of nuclear spins has yet to be explored further. This article demonstrates that the hyperfine coupling, which consists of Fermi contact and dipolar interactions, can mediate the application of spin-orbit torques acting on nuclear spins. Our starting point is a sizable nuclear spin in a metal with electronic spin accumulation. Then, via the hyperfine interactions, the nuclear spin modifies the an electronic spin density. The reactions to the equilibrium and nonequilibrium components of the spin density is a torque on the nucleus with field-like and damping-like components, respectively. Thisnuclearspin-orbittorqueis a step toward stabilizing and controlling nuclear magnetic momenta, in magnitude and direction, and realizing nuclear spintronics.

Manifestation of charge/orbital order and charge transfer in temperature-dependent optical conductivity of single-layered Pr0.5Ca1.5MnO4.

Half-doped single-layered manganite, [Formula: see text] has shown a charge/orbital order of the e g electrons and CE-type spin order of the t 2g electrons of the Mn ions. A previous experimental study on that system, supported by a simple modelling, has suggested that the charge/orbital ordering play an important role in governing the temperature dependence of optical conductivity of a broad peak around 0.7-0.8 eV. In addition, another peak around 3.5 eV, which is less sensitive to temperature, has been attributed to the charge transfer from O-p  to Mn-e g orbitals. Nevertheless, the theoretical explanation was incomplete as the role of O-p  orbitals was not considered in the model. In this paper, we propose to improve the model by incorporating both Mn-e g and O-p  orbitals. We assume the existence of charge/orbital ordering and investigate how this ordering as well as the charge-transfer phenomenon control the temperature dependence of the optical conductivity. Our results reveal the charge/orbital-ordering peak in the region 0.7-1.2 eV, which is blue-shifted with decreasing temperature, and the charge-transfer peak around 3.5 eV, which is less sensitive to temperature. The capability of our model to capture the general profile and temperature dependence of the optical conductivity suggests the validity of our theory.

Voltage Control of Rare-Earth Magnetic Moments at the Magnetic-Insulator-Metal Interface.

The large spin-orbit interaction in the lanthanides implies a strong coupling between their internal charge and spin degrees of freedom. We formulate the coupling between the voltage and the local magnetic moments of rare-earth atoms with a partially filled 4f shell at the interface between an insulator and a metal. The rare-earth-mediated torques allow the power-efficient control of spintronic devices by electric-field-induced ferromagnetic resonance and magnetization switching.