Dec 8 – 10, 2020 Online only
Online event
Europe/Berlin timezone

Magnetic dynamics in the single-domain state of the cubic helimagnet ZnCr2Se4

Dec 9, 2020, 2:30 PM
3h 30m
Online event

Online event

Speaker

Dmytro Inosov (TU Dresden)

Description

Anisotropic low-temperature properties of the cubic helimagnet ZnCr2Se4 in the single-domain spin-spiral state are investigated by a combination of neutron scattering, thermal conductivity,and dilatometry measurements. In an applied magnetic field, neutron spectroscopy shows a complex and nonmonotonic evolution of the spin-wave spectrum across the quantum-critical point that separates the spin-spiral phase from the field-polarized ferromagnetic phase at high fields. A tiny spin gap of the pseudo-Goldstone magnon mode, observed at wave vectors that are structurally equivalent but orthogonal to the propagation vector of the spin helix, vanishes at this quantum critical point, restoring the cubic symmetry in the magnetic subsystem. The anisotropy imposed by the spin helix has only a minor influence on the lattice structure and sound velocity, but has a much stronger effect on the heat conductivities measured parallel and perpendicular to the magnetic propagation vector. Anisotropic thermal transport is magnetic in origin and highly sensitive to an external magnetic field. We also report long-time thermal relaxation phenomena, revealed by capacitive dilatometry, which are due to magnetic domain motion related to the destruction of the single-domain magnetic state. Our results can be generalized to a broad class of helimagnetic materials in which a discrete lattice symmetry is spontaneously broken by the magnetic order.

Primary authors

Dmytro Inosov (TU Dresden) Y. O. Onykiienko (TU Dresden) Y. V. Tymoshenko (TU Dresden) A. Akopyan (University of Miami) D. P. Shukla (University of Miami) M. Doerr (TU Dresden) S. Zherlitsyn (Helmholtz-Zentrum Dresden-Rossendorf) D. Voneshen (ISIS, Rutherford Appleton Laboratory) M. Boehm (Institut Laue-Langevin) V. Tsurkan (University of Augsburg) V. Felea (Inst. of Applied Physics, Acad. Sci. Moldova) A. Loidl (University of Augsburg) J. L. Cohn (University of Miami)

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