Lattice vibrations boost demagnetization entropy in a shape-memory alloy

P. J. Stonaha, M. E. Manley, N. M. Bruno, I. Karaman, R. Arroyave, N. Singh, D. L. Abernathy, S. Chi

    Research output: Contribution to journalArticlepeer-review

    21 Scopus citations

    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 the Curie temperature (TC), the material exhibits an anomalous increase in phonon entropy of 0.22±0.04kB/atom, which is ten times larger than expected from conventional thermal expansion. This transition is accompanied by an abrupt softening of the transverse optic phonon. We present first-principles calculations showing a strong coupling between lattice distortions and magnetic excitations.

    Original languageEnglish
    Article number140406
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume92
    Issue number14
    DOIs
    StatePublished - Oct 7 2015

    Funding

    FundersFunder number
    National Science Foundation
    Directorate for Mathematical and Physical Sciences0805293, 0844082
    Directorate for Mathematical and Physical Sciences

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