Aurelien Manchon

Spin-transfer torque generated by a topological insulator

Magnetic devices are a leading contender for the implementation of memory and logic technologies that are non-volatile, that can scale to high density and high speed, and that do not wear out. However, widespread application of magnetic memory and logic devices will require the development of efficient mechanisms for reorienting their magnetization using the least possible current and power. There has been considerable recent progress in this effort; in particular, it has been discovered that spin–orbit interactions in heavy-metal/ferromagnet bilayers can produce strong current-driven torques on the magnetic layer, via the spin Hall effect in the heavy metal or the Rashba–Edelstein effect in the ferromagnet. In the search for materials to provide even more efficient spin–orbit-induced torques, some proposals have suggested topological insulators, which possess a surface state in which the effects of spin–orbit coupling are maximal in the sense that an electron’s spin orientation is fixed relative to its propagation direction. Here we report experiments showing that charge current flowing in-plane in a thin film of the topological insulator bismuth selenide (Bi2Se3) at room temperature can indeed exert a strong spin-transfer torque on an adjacent ferromagnetic permalloy (Ni81Fe19) thin film, with a direction consistent with that expected from the topological surface state. We find that the strength of the torque per unit charge current density in Bi2Se3 is greater than for any source of spin-transfer torque measured so far, even for non-ideal topological insulator films in which the surface states coexist with bulk conduction. Our data suggest that topological insulators could enable very efficient electrical manipulation of magnetic materials at room temperature, for memory and logic applications.

New perspectives for Rashba spin-orbit coupling

In 1984, Bychkov and Rashba introduced a simple form of spin-orbit coupling to explain the peculiarities of electron spin resonance in two-dimensional semiconductors. Over the past 30 years, Rashba spin-orbit coupling has inspired a vast number of predictions, discoveries and innovative concepts far beyond semiconductors. The past decade has been particularly creative, with the realizations of manipulating spin orientation by moving electrons in space, controlling electron trajectories using spin as a steering wheel, and the discovery of new topological classes of materials. This progress has reinvigorated the interest of physicists and materials scientists in the development of inversion asymmetric structures, ranging from layered graphene-like materials to cold atoms. This Review discusses relevant recent and ongoing realizations of Rashba physics in condensed matter.

First-principles investigation of the very large perpendicular magnetic anisotropy at Fe|MgO and Co|MgO interfaces

The perpendicular magnetic anisotropy (PMA) arising at the interface between ferromagnetic transition metals and metallic oxides are investigated via first-principles calculations. In this work very large values of PMA up to 3 erg/cm

Current induced torques and interfacial spin-orbit coupling: semiclassical modeling

^2

Analysis of oxygen induced anisotropy crossover in Pt/Co/MOx trilayers

at Fe

Diffusive spin dynamics in ferromagnetic thin films with a Rashba interaction.

|

Relativistic Néel-order fields induced by electrical current in antiferromagnets.

MgO interfaces are reported in agreement with recent experiments. The origin of PMA is attributed to overlap between O-

Spin-orbit torques in Co/Pd multilayer nanowires

p_z

Quantum spin/valley Hall effect and topological insulator phase transitions in silicene

and transition metal

X-ray analysis of the magnetic influence of oxygen in Pt/Co/AlOx trilayers

d_{z^2}