Excitations and Magnetic Properties of Rare-Earth Al2 Compounds

Per Bak

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    Magnetic excitation spectra, measured by inelastic neutron scattering, and single-crystal magnetization curves of rare-earth AI2 compounds are analysed using a Hamiltonian including 4th and 6th order crystal field terms and an isotropic exchange interaction between the magnetic ions. The magnetic excitations - "excitons" - are transitions between single-ion. atomic levels propagating through the lattice via the exchange interaction. In NdAl2 dispersion relations of excited mean-field states are described for the first time. A double peak structure in the neutron spectrum of TbAl2 is interpreted as a new effect: the magnon- exciton interaction. To calculate the excitation energies a Green's function theory was evaluated. A detailed microscopic description of the magnetic anisotropy of NdAl2. PrAl2 TbAl2, and ErAl2 is given in terms of two temperature and field independent crystal field parameters by means of a two-dimensional mean-field theory. The crystal field parameters are shown to behave systematically throughout the entire rar e earth AU series, indicating that the effective charge distribution around the magnetic ions is independent of the particular rare earth constituent.
    Original languageEnglish
    Place of PublicationRoskilde, Denmark
    PublisherRisø National Laboratory
    Number of pages62
    ISBN (Print)8755002757
    Publication statusPublished - 1974
    SeriesDenmark. Forskningscenter Risoe. Risoe-R


    • Risø-R-312
    • Risø report 312
    • Risø-312


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