Topological orbital magnetic moments
CFM Seminars
 Speaker

Manuel dos Santos Dias
 When

2018/09/26
14:00  Place
 CFM Auditorium
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Host: Julen Ibañez (CFM)
The magnetic moment carried by electrons in a condensed matter system has two
components: the one originating from its spin and the one originating from its
orbital motion. The spin magnetic moment arises from the first of Hund’s
rule in most cases, which is also partially satisfied in magnetic solids.
There are two wellknown mechanisms for the formation of the orbital magnetic
moment: the second of Hund’s rules, which applies only to atomiclike
electron orbitals, and spinorbit coupling, which lifts the quenching of the
orbital moment in a magnetic solid.
Here we discuss a third mechanism that leads to the formation of orbital
magnetic moments: magnetic structures with a special topology, where the spin
magnetic moments do not all lie in the same plane [1]. We illustrate the basic
aspects considering magnetic trimers as model systems, e.g. Fe3 on the Cu(111)
surface. The symmetry of the effect is established, showing how to distinguish
the topological and the spinorbit contributions. We then focus on the
implications of the topological orbital moments for single magnetic skyrmions
formed in Pd/Fe/Ir(111), using firstprinciples electronic structure
calculations and a simplified tightbinding model. We propose that the
topological orbital moments could enable detecting and distinguishing
skyrmions from antiskyrmions by soft xray spectroscopy [2], as an
alternative and complementary technique to transport measurements of the
topological Hall effect, magnetic force microscopy or scanning tunneling
microscopy.