Gd3+ Spin--Phonon Interactions in Rare-Earth Fluoride Crystals

M.L. Paradowski and L.E. Misiak Institute of Physics, Marie Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

Received: April 19, 2002

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The X-band EPR study of Gd3+-doped LaF3, La0.9Ce0.1 F3, La0.9Nd0.1F3, LiYF4 and LiY0.9Yb0.1F4 single crystals in the temperature range 4.2--295 K was carried out in order to investigate the Gd3+ spin--phonon interactions. Spin-Hamiltonian parameters are analysed in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. The 4f7 electron--phonon interactions can be described by the Debye model. It is suggested, from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters, that the rotational contributions are much smaller than those from the strain. Temperature-induced distortions of the crystal field, as well as these distortions caused by the La3+/Nd3+ and Y3+/ Yb3+ substitutions, influence significantly the 4f7 electron--phonon interactions. The coupling constant K2 of 4f7 electrons to the whole phonon spectrum of the crystal lattice is stronger in the LaF3, La0.9 Ce0.1F43, La0.9Nd0.1F3 with larger temperature-induced distortion of the Gd3+ site symmetry than in LiYF4, LiY0.9Yb0.1F4. Our results are compared with those for Gd3+-doped RbCdF3 and PbF2 single crystals.

DOI: 10.12693/APhysPolA.102.373 PACS numbers: 63.20.Kr, 76.30.Kg