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1

Gd^{3+}-RE^{3+} Exchange Interactions in Rare-Earth Fluoride Crystals (RE = Ce, Nd, Yb)

100%

Paradowski M., Misiak L.

Acta Physica Polonica A

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2004

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vol. 105

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issue 5

445-457

EN

The investigation of Gd^{3+}-doped LaF_3, La_{0.9}Ce_{0.1}F_3, CeF_3, La_{0.9}Nd_{0.1}F_3, LiYF_4, and LiY_{0.9}Yb_{0.1}F_4 single crystals at 4.2 K was carried out in order to study the Gd^{3+}-RE^{3+} exchange interactions (RE = Ce, Nd, Yb). The exchange interactions were estimated by the application of the molecular-field model at liquid-helium temperature, using the g shift from the isostructural diamagnetic hosts LaF_3 and LiYF_4 to the paramagnetic hosts. The lattice dynamics is studied by analysing spin-Hamiltonian parameters in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. It is suggested from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters that the rotational contributions influence the exchange interactions significantly. Further, the distortions caused by the La^{3+}/Ce^{3+}, La^{3+}/Nd^{3+}, and Y^{3+}/Yb^{3+} substitutions affect significantly the 4f^7 electron-phonon interactions, as well as the exchange interactions. The magnitude of the isotropic exchange interactions is larger for more symmetrical charge distribution of the 4f^7 shell.

2

EPR of Gd^{3+}-Doped La_{0.9}Nd_{0.1}F_{3} Crystal: Spin-Phonon Interactions and Spin-Lattice Relaxations

100%

Paradowski M., Misiak L.

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vol. 95

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issue 3

367-380

EN

The X-band EPR study of Gd^{3+}-doped La_{0.9}Nd_{0.1}F_{3} single crystal in the temperature range 4.2-295 K is carried out in order to investigate crystal field effects, the Gd^{3+} spin-phonon interactions, as well as Gd^{3+} and Nd^{3+} spin-lattice relaxation times. The local distortions at 4.2 K of the positions of the eight F^{-} ions surrounding the Gd^{3+} ion in the La_{0.9}Nd_{0.1}F_{3} crystal were determined from comparison of the theoretical with the experimental spin-Hamiltonian parameters. The spin-phonon interactions can be described by the Einstein model, which better characterizes the behavior of paramagnetic centers in LaF_{3} and La_{0.9}Nd_{0.1}F_{3} crystals than 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.

3

Gd^{3+} Spin-Phonon Interactions in Rare-Earth Fluoride Crystals

100%

Paradowski M., Misiak L.

Acta Physica Polonica A

|

2002

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vol. 102

|

issue 3

373-384

EN

The X-band EPR study of Gd^{3+}-doped LaF_3, La_{0.9}Ce_{0.1}F_3, La_{0.9}Nd_{0.1}F_ 3, LiYF_4 and LiY_{0.9}Yb_{0.1}F_4 single crystals in the temperature range 4.2-295 K was carried out in order to investigate the Gd^{3+} 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 4f^7 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 La^{3+}/Nd^{3+} and Y^{3+}/Yb^{3+} substitutions, influence significantly the 4f^7 electron-phonon interactions. The coupling constant K_2 of 4f^7 electrons to the whole phonon spectrum of the crystal lattice is stronger in the LaF_3, La_{0.9}Ce_{0.1}F_3, La_{0.9}Nd_{0.1}F_3 with larger temperature-induced distortion of the Gd^{3+} site symmetry than in LiYF_4, LiY_{0.9}Yb_{0.1}F_4. Our results are compared with those for Gd^{3+}-doped RbCdF_3 and PbF_2 single crystals.

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3 Acta Physica Polonica A

1 2004

1 2002

1 1999

3 Misiak L.

3 Paradowski M.

Gd^{3+}-RE^{3+} Exchange Interactions in Rare-Earth Fluoride Crystals (RE = Ce, Nd, Yb)

EPR of Gd^{3+}-Doped La_{0.9}Nd_{0.1}F_{3} Crystal: Spin-Phonon Interactions and Spin-Lattice Relaxations

Gd^{3+} Spin-Phonon Interactions in Rare-Earth Fluoride Crystals