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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:45 |
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Conference: Bucharest University Faculty of Physics 2006 Meeting
Section: Atomic and Molecular Physics; Astrophysics
Title:
Multifrequency Electron Paramagnetic Resonance of Rare Earth Trace Impurities in PbWO4 Single Crystals. High Field effects
Authors:
F.F. Popescu(1)(2), M. Martinelli(2) , L.A. Pardi(2) , V. Bercu(2)(3), S.V. Nistor(4), M. Stefan(4)
P. Suraianu, Z. Petcu, L. Parmac
Affiliation:
(1)Department of Physics, University of Bucharest, Magurele, Ro-76900, Bucharest.
(2)Istituto per i Processi Chimico-Pisici, CNR, via G. Moruzzi 1, 56124 Pisa.
(3)Dipartimento di Fisica Enrico Fermi, Università di Pisa, via F .Buonarroti 2, I-56127 Pisa.
(4)National Institute for Materials Physics, Ro-077125, Magurele, Bucharest
E-mail
ffpopescu@k.ro
Keywords:
Abstract:
An EPR investigationof rare earth trace impurities in PbWO4 single crystals was carried out at 4.2 1/2 and a large orbital contribution[1]. Consequently these paramagnetic ions exhibits a ground doublet and other closed excited doublets. In many cases, this zero-field splitting is small to be measured by optical spectroscopy, while the susceptibility measurements are not suitable to locate them with a reasonable precision. The effective g=1/2 factors exhibit important frequency and magnetic field dependences. They correspond within errors, to a Hamiltonian appropriate to tetragonal symmetry without orthorhombic distortion. Unlike the conventional microwave EPR spectroscopy, at high fields these g effective values depend not only on the polar angle between the magnetic field B and the tetragonal axis, but also on the azimuthal angle j between B and the binary axes of the molecular complex. These dependences include additional terms proportional to (B)2m(cos 4φ)n, where m ³ n are natural numbers. They show that in the present experiment, the Zeeman interaction is comparable with the zero-field splitting of the ground manifold. For Gd3+ an important temperature, and frequency dependence of the linewidths was observed. This dependence was explained by considering the spin-lattice relexation effects [2].
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