40th CEMS Colloquium
Speaker
Dr. Istvan Kezsmarki (Budapest University of Technology and Economics)
Date
17:30 - 18:30, June 22, 2016 (Wednesday)
Venue
BSI Ikenohata Building 3F, RIKEN
Title
Néel-type skyrmions with polar dressing in multiferroic lacunar spinels
Abstract
GaV4S8, a member of the lacunar spinel family, is the first known example of skyrmion-host materials with non-chiral but polar crystal structure. This compound is a magnetic semiconductor with a rhombohedral crystal symmetry (R3m) and an easy-axis magnetic anisotropy. In this compound we observed the formation of a Néel-type skyrmion lattice, which exists over a broad temperature range. This is in contrast to Bloch-type skyrmions found in chiral magnets, which are stabilized by thermal fluctuations in small pockets of the phase diagram. We found that the orientation of these Néel-type skyrmions is not controlled by the external magnetic field, but instead confined to the magnetic easy axis. Another isostructural compound of this family is GaV4Se8, which is characterized by a weaker anisotropy. In this material the Néel-type skyrmion state is even more extended, namely it is the first bulk compound where the skyrmion lattice is stable down to zero temperature. We found that the skyrmion phase can also be stabilized in GaV4S8 by moderate hydrostatic pressures. Due to the polar nature of these crystals, the Néel-type magnetic skyrmions wear a ferroelectric dressing and exhibit strong static and dynamic magnetoelectric effects.
