Magnetic field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4
| Autor: | Dmytro S. Inosov, Sergei Zherlitsyn, Dharmendra Shukla, D. J. Voneshen, Y. O. Onykiienko, Martin Boehm, Vladimir Tsurkan, Narayan Prasai, Alois Loidl, A. Akopyan, Mathias Doerr, Y. V. Tymoshenko, Joshua L. Cohn, Denis Gorbunov, V. Felea |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Condensed matter physics Magnetic domain Magnon Relaxation (NMR) 02 engineering and technology 021001 nanoscience & nanotechnology Thermal conduction 01 natural sciences Magnetic field Ferromagnetism Quantum critical point 0103 physical sciences Condensed Matter::Strongly Correlated Electrons 010306 general physics 0210 nano-technology Spin-½ |
| Zdroj: | Physical Review B. 102 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | Anisotropic low-temperature properties of the cubic spinel helimagnet $\mathrm{Zn}{\mathrm{Cr}}_{2}{\mathrm{Se}}_{4}$ in the single-domain spin-spiral state are investigated by a combination of neutron scattering, thermal conductivity, ultrasound velocity, 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. The thermal transport is anisotropic at $T\ensuremath{\lesssim}2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, highly sensitive to an external magnetic field, and likely results directly from magnonic heat conduction. 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, initially stabilized in the sample by the application and removal of magnetic field. 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. |
| Databáze: | OpenAIRE |
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