EventDetails

Speaker:
Prof. Dr. Sebastian T. B. Goennenwein

Transverse Transport Effects in Magnetic Nanostructures

About 140 years ago, Edwin Hall observed that in a metal exposed to a magnetic field, a charge current is accompanied not only by a voltage drop along the current, but also by an electric field transverse to both the current flow and the magnetic field. Since then, the Hall effect is the prototypical ‘transverse transport’ effect. The Hall effect unambiguously shows that charge transport in solids must be discussed using a tensorial quantity, e.g., the conductivity tensor. Since similar arguments also apply to heat and to spin transport effects in solids, a whole set of transverse transport phenomena is established and exploited today.

In the talk, I will first focus on charge-based transverse transport effects in magnetically ordered materials. More specifically, I will show that characteristic transverse ‘Hall’ electric fields can arise not only due to an externally applied magnetic field, but also from the internal magnetization or spin structure of a solid. These effects are referred to as anomalous Hall effect and topological Hall effect, respectively, in the literature. Together with their thermal counterparts – the anomalous and the topological Nernst effect – these phenomena allow probing the spin structure of individual magnetic nanostructures.

In the second part of the talk, I will switch to spin-based transverse transport in magnet/metal heterostructures. Here, the so-called spin Hall effect has emerged as a powerful tool for the generation and detection of pure spin currents. We use this approach in particular for the investigation of magnon spin currents in magnetic insulators. I will show how the diffusion of magnons in an electrically insulating magnet can be detected and quantified using spin Hall physics, and present first steps towards magnon drift transport.