Mikhail Titov: Anisotropy induced by spin-orbit interactions: new insights to chiral magnetism and magnetization dynamics

In this talk I overview our recent progress in understanding the role of strong spin-orbit interactions of conduction electrons in magnetic systems. First, I present a general point group classification of linear-in-gradient terms in micromagnetic energy that is designed to revise the seminal work of Bogdanov and Yablonskii. In particular, I will demonstrate that, apart from Dzyaloshinskii-Moria interactions represented by Lifshitz invariants (LI), there exists non-LI contributions in micromagnetic energy. Such contributions are shown to be highly relevant in stabilizing non-collinear magnetic order at least in some crystals. I will also demonstrate that in crystals defined by the point groups Td, Dh3, and Ch3, the Lifshitz-Invariant terms are forbidden and non-LI terms become most important. I will present a new model for a chiral magnet in Td point group symmetry. I will present a microscopic analysis of non-LI terms in a generalized 2D Rashba ferromagnet.

In the second part of my talk, I present a detailed study of current induced phenomena in 2D Rashba ferromagnet. In particular I will show how Gilbert damping and in-plane spin-transfer torques acquire strong anisotropy due to spin-orbit interaction. I will also derive a general relation between these quantities that make the speed of magnetic textures universally equal to the drift velocity of conduction electrons in the Rashba model. At the end of my talk I will compare our microscopic results to the standard phenomenological equations on magnetization dynamics to make some further insights.