TY - JOUR
T1 - Magnetic field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4
AU - Inosov, D. S.
AU - Onykiienko, Y. O.
AU - Tymoshenko, Y. V.
AU - Akopyan, A.
AU - Shukla, D.
AU - Prasai, N.
AU - Doerr, M.
AU - Gorbunov, D.
AU - Zherlitsyn, S.
AU - Voneshen, D. J.
AU - Boehm, M.
AU - Tsurkan, V.
AU - Felea, V.
AU - Loidl, A.
AU - Cohn, J. L.
N1 - Funding Information:
We would like to thank C. Hess, S.-C. Lee, D. Efremov, A. Yaresko, and M. Vojta for stimulating discussions and X.-F. Sun for sharing their recently published thermal-conductivity data . This project was funded by the German Research Foundation (DFG) through the Collaborative Research Center SFB 1143 in Dresden [projects C03 (D.S.I.) and A06 (S.R.)], individual research Grant IN 209/4-1, and the Transregional Collaborative Research Center TRR 80 (Augsburg, Munich, Stuttgart). T.M. and R.T. acknowledge support from DFG-SFB 1170 ToCoTronics (project B04) and the ERC Starting Grant ERC-StG-Thomale-336012 “Topolectrics”. Work at the University of Miami was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award No. DE-SC0008607.
PY - 2020/11/30
Y1 - 2020/11/30
N2 - Anisotropic low-temperature properties of the cubic spinel helimagnet ZnCr2Se4 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 T2K, 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.
AB - Anisotropic low-temperature properties of the cubic spinel helimagnet ZnCr2Se4 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 T2K, 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.
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U2 - 10.1103/PhysRevB.102.184431
DO - 10.1103/PhysRevB.102.184431
M3 - Article
AN - SCOPUS:85097170349
VL - 102
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 2469-9950
IS - 18
M1 - 184431
ER -