Thin film magnetic B20 silicides and germanides: anomalous and topological Hall effects

Date

Jan 20, 2015

Time

4:40 PM - 6:10 PM

Speaker

Prof. Dr. Christopher Marrows

Affiliation

University of Leeds

Series

TUD Physikalisches Kolloquium

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Prof. Dr. Carsten Timm, Fachrichtung Physik

Description

The coupling of electron spin to real-space magnetic textures leads to a varie­ty of interesting magnetotransport effects. Chiral spin textures, such as the skyrmion lattices found in B20-lattice magnets give rise, via real-space Berry phases and associated emergent magnetic fields, to the topological Hall effect. Here we show that B20-ordered Fe0.7Co0.3Si epilayers grown on Si(111) substrates display a giant topological Hall effect, ways larger than in MnSi and MnGe, due to the combination of three favorable properties: they have (a) a high spin-polarization, (b) a large ordinary Hall coefficient, and (c) a large emergent magnetic field. Moreover, they show enhanced ordering temperatures due to the presence of epitaxial strain. Also, we have prepared thin films of B20-phase FeGe and studied their magnetotransport properties. We find three distinct regimes in the high field MR behavior: it is positive up to ~100 K (Lorentz force), negative and linear up to about 225 K (magnon scattering), and then negative, large, and with positive curvature (local moment scattering). The anomalous Hall resistivity scales quadratically with longitudinal resistivity, ruling out a significant role for skew scattering. Moreover, we observe a modest topological Hall effect of about 100 nWcm. That such effects can be found in materials grown in thin film form on commercial silicon wafer bodes well for skyrmion-based spintronics.

Links

• http://tu-dresden.de/veranstaltungen/termin?id=TUD5432781e4d7c9

Last modified: Jan 20, 2015, 8:41:47 AM