Magnon dispersion relation and exchange interactions in MnF2

O. Nikotin, Per-Anker Lindgård, O. W. Dietrich

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    Abstract

    The magnon dispersion relation for MnF2 at 4·2 °K has been measured by means of the triple-axis neutron scattering technique along the symmetry lines in the (010) plane of the Brillouin zone. Using an exact dipole model, the three nearest-neighbour exchange constants were found to be J1 = 0·028 ± 0·001 mev, J2 = -0·152 ± 0·001 mev and J3 = -0·004 ± 0·001 mev. The second moment was also calculated with this model. The density of magnon states was evaluated by applying a six-parameter simulation of the dispersion surface. The critical points in the density of states agree well with those obtained by optical double-magnon experiments, whereas the detailed shape of the density of states differs significantly, indicating that the effect of magnon-magnon interactions rather than that of distant-neighbour exchange is of primary importance in the optical measurements.

    Original languageEnglish
    JournalJournal of Physics C: Solid State Physics
    Volume2
    Issue number7
    Pages (from-to)1168-1173
    ISSN0022-3719
    DOIs
    Publication statusPublished - 1969

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