  Inelastic neutron scattering measurements were performed on single crystals
of the antiferromagnetic compound Mn5Si3 in order to investigate the relation
between the spin dynamics and the magneto-thermodynamic properties. It is shown
that among the two stable antiferromagnetic phases of this compound, the high
temperature one has an unusual magnetic excitation spectrum where propagative
spin-waves and diffuse spin-fluctuations coexist. Moreover, it is evidenced
that the inverse magnetocaloric effect of Mn5Si3, the cooling by adiabatic
magnetization, is associated with field induced spin-fluctuations.
