Chiral magnets do the twist

Datum

30.10.2012

Zeit

16:40 - 18:10

Sprecher

P D Dr. Markus Garst

Zugehörigkeit

Universität zu Köln

Serie

TUD Physikalisches Kolloquium

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Beschreibung

Chiral magnets can gain energy by twisting the magnetization on a length scale determined by spin - orbit coupling resulting in twisted magnetic textures like helices. Particularly interesting are the cubic chiral magnets encompassing the metals MnSi, FeGe, the se miconductor Fe 1 - x Co x Si and the insulator Cu 2 OSeO 3 . The magnetic transition in these compounds corresponds to a weak crystallization process where the reciprocal lattice vector of the magnetic order is inversely proportional to the twist length. Consequentl y, the transition from the paramagnet to the helimagnetic order - a quasi one - dimensional magnetic crystal - is driven first - order by fluctuations. At finite magnetic field, a quasi two - dimensional magnetic crystal is realized consisting of a regular arran gement of so - called skyrmions. The topological nature of these objects gives rise to an efficient coupling to spin - currents resulting in observable spintronic phenomena at low current densities. As the spin of the itinerant electrons constantly adapts to t he skyrmion texture, its orbital motion experiences an artificial magnetic field of one flux quantum per skyrmion that contributes to the Hall effect. If the applied electric current exceeds a threshold value, the depinning of skyrmions results in a moving magnetic texture that induces an artificial electric field via Faraday's law of induction. The resulting emergent artifical electrodynamics promises to become an interesting playground for novel spintronic phenomena.

Letztmalig verändert: 01.11.2012, 08:36:35