Spin Dynamics Of The Magnetocaloric Compound Mnfe4si3

The magnetic excitation spectrum of the magnetocaloric compound MnFe4Si3 has been investigated by means of polarized and unpolarized inelastic neutron scattering on single crystals. Spectra were collected in the ferromagnetic phase (T-C approximate to 305 K), as well as in the paramagnetic state, in order to understand the nature of the magnetism in MnFe4Si3. Spin-wave measurements at 1.5 K reveal a strong anisotropy of the magnetic exchange interactions along the (h00) and (00l) reciprocal directions of the hexagonal system, which also manifests itself in the q-dependent linewidths in the paramagnetic state. The correlation lengths indicate a short-range order, while the average linewidth is of the order of k(B)T(C) pointing to a behavior typical of many ferromagnets. In addition, the in- and out-of-plane spin fluctuations are found to be isotropic around T-C and can be suppressed by a magnetic field of 2 T.