Publication Type
Journal
Journal Name
Physical Review Letters
Publication Date
Page Number
140406
Volume
92
Issue
14
Abstract
Magnetocaloric (MC) materials present an avenue for chemical-free, solid state refrigeration through cooling via adiabatic demagnetization. We have used inelastic neutron scattering to measure the lattice dynamics in the MC material Ni45Co5Mn36.6In13.4. Upon heating across TC, the material exhibits an anomalous increase in phonon entropy of 0.17±0.04 k_B/atom, which is nine times larger than expected from conventional thermal expansion. We find that the phonon softening is focused in a transverse optic phonon, and we present the results of first-principle calculations which predict a strong coupling between lattice distortions and magnetic excitations.
