Neel-type Skyrmion Lattice with Ferroelectric Vortex Cores in a Polar Magnetic Semiconductor

Date

May 12, 2015

Time

9:30 AM - 10:30 AM

Speaker

Dr. Istvan Kezsmarki

Affiliation

Budapest University of Technology and Economics, Department of Physics

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Grit Rötzer

Description

Following the early prediction of the skyrmion lattice (SkL)- a periodic array of spin vortices - by Bogdanov and coworkers [1], it has been observed recently in various magnetic crystals, mostly with chiral structure [2]. Although non-chiral but polar crystals with C_nv symmetry were identified as ideal SkL hosts in pioneering theoretical studies, this archetype of SkL has remained experimentally unexplored. We report the discovery of a SkL in the polar magnetic semiconductor GaV4S8 with rhombohedral (C_3v) symmetry and easy axis anisotropy [3]. The SkL exists over an unusually broad temperature range compared with other bulk crystals and the orientation of the vortices is not controlled by the external magnetic field but instead confined to the magnetic easy axis. Supporting theory attributes these unique features to a new Neel-type of SkL describable as a superposition of spin cycloids in contrast to the Bloch-type SkL in chiral magnets described in terms of spin helices. We found that the strong orientational confinement of the vortices ensures the robustness of two distinct skyrmionic states with a core magnetization pointing either up or down the easy axis. This may facilitate a unique magnetic control of the SkL by magnetic fields applied perpendicular to the vortex cores in contrast to cubic helimagnets where vortex cores instantaneously co-align with the magnetic field. In addition, the spin-driven electric polarization associated with the Neel-type skyrmion cores in GaV4S8 may be exploited for a non-dissipative electric field control of the SkL [4]. [1] A. N. Bogdanov and A. Hubert, J. Magn. Magn. Mater. 138, 255 (1994). [2] S. Mühlbaueret al., Science 323, 915 (2009). [3] I. Kezsmarki et al., http://arxiv.org/abs/1502.08049 [4] E. Ruff et al., http://xxx.lanl.gov/abs/1504.00309

Links

• Seminars at the IFW

Last modified: May 12, 2015, 9:49:12 AM