期刊
PHYSICA B-CONDENSED MATTER
卷 345, 期 1-4, 页码 124-127出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.physb.2003.11.037
关键词
weak ferromagnets; Dzyaloshinskii-Moriya interaction; spin fluctuations; polarized neutron scattering
Polarized neutrons were used to determine the antisymmetric part of the magnetic dynamical susceptibility chi(Q,omega) in the weak ferromagnet MnSi. We find that above the Curie temperature T-c the spin fluctuations are incommensurate with the chemical lattice and that chi(Q,omega) depends on the polarization of the incident neutron beam P-1 like (Q (.) P-1) where Q is the scattering vector. Because the crystal structure of MnSi is non-centrosymmetric we interpret these results in terms of the antisymmetric Dzyaloshinskii-Moriya interaction which yields a non-zero contribution to the antisymmetric part of chi(Q,omega). Additional measurements performed below T-c show that in zero field the spin excitations in MnSi have also in the ordered phase a chirality. With increasing external magnetic field B, the magnetic excitations evolve from helical to ferromagnetic-like. In the field-induced phase where the magnetic moments are aligned, magnon annihilation and creation are observed for +/-P-1//B, respectively. (C) 2003 Elsevier B.V. All rights reserved.
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