MRSej, Vol. 6, No.1, pp.1-9, 2004
EFFECT OF DIAMAGNETIC DILUTION ON SPIN DYNAMICS IN MANGANITES
V.A. Atsarkin1, V.V. Demidov1, D.G. Gotovtsev1, N.E. Noginova1,2
1 Institute of Radio Engineering and Electronics RAS, 125009 Moscow , Russia
2 Norfolk State University, Norfolk, VA 23504, USA
In the magnetically diluted LaMnxGa1-xO3 single crystals, the EPR spectra of the Mn ions (at 0.02 <= x <= 1), as well as NMR and nuclear spin-lattice relaxation of 69Ga and 71Ga nuclei have been investigated. The analysis of the EPR spectra enabled one to follow the exchange narrowing effect to the point of appearance of a single Lorentzian line at x >= 0.2. The transition from the antiferromagnetic to ferromagnetic type of spin ordering is confirmed under condition of the diamagnetic dilution with Ga, starting from x = 0.8. At x = 0.1, unusual broadening and splitting of the EPR spectrum are found upon cooling; this can be assigned to the effect of thermally activated internal motion with characteristic energy Ea of about 50 meV. The study of nuclear spin-lattice relaxation was performed in the temperature range of 190-390 K. The obtained data support the existence of the internal motion with the same value of Ea . This motion can be attributed to thermally activated re-orientations of the eg electron orbitals of the Mn3+ ions subjected to the Jahn-Teller effect.
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