Magnetic field dependence of chiral fluctuations in MnSi

• Published in: Physica. B, Condensed matter Vol. 345; no. 1; pp. 124 - 127
• Main Authors: Roessli, B., Böni, P., Fischer, W.E., Endoh, Y.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2004; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dzyaloshinskii–Moriya interaction; Exact sciences and technology; Magnetic properties and materials; Physics; Polarized neutron scattering; Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.); Spin fluctuations; Weak ferromagnets; Dzyaloshinskii–Moriya interaction; Polarized neutron scattering; Spin fluctuations; 71.70.Ej; 71.20.Lp; 75.25.+z; Weak ferromagnets; Manganese silicides; Non centrosymmetric crystals; Phase diagrams; Spin waves; Inorganic compounds; Polarized neutron; Transition element compounds; 71.20.Lp Weak ferromagnets; Magnetic field effects; Ferromagnetic materials; Dynamic properties; Experimental study; Neutron diffusion; Magnetic susceptibility; Inelastic scattering; Weak ferromagnetism; Dzyaloshinskii-Moriya interaction; Chirality
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2003.11.037

Polarized neutrons were used to determine the antisymmetric part of the magnetic dynamical susceptibility
χ(
Q
,ω)
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
χ(
Q
,ω)
depends on the polarization of the incident neutron beam
P
i
like
(
Q
·
P
i)
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
χ(
Q
,ω)
. 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
i//
B
, respectively.