Inhomogeneity of the ferromagnetic state of (La1−x Srx)1−δMnO3 perovskites according to 139La and 55Mn NMR data
| Autor: | T. N. Tarasenko, Miroslav Maryško, V. I. Kamenev, V. D. Doroshev, V. A. Borodin, M. M. Savosta, Anton S. Mazur |
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| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Journal of Experimental and Theoretical Physics. 97:573-586 |
| ISSN: | 1090-6509 1063-7761 |
| DOI: | 10.1134/1.1618342 |
| Popis: | The paper presents results obtained in studying 139La and 55Mn nuclear magnetic resonance spectra and nuclear magnetic relaxation in the temperature range 21–220 K augmented by data on the magnetic and transport properties of ferromagnetic (La1−x Srx)1−δMnO3 manganites (x=0, 0.075, and 0.125, δ≈0.0−0.05). The transition from the ferromagnetic state with semiconductor-type conductivity to the ferromagnetic state with metallic conductivity as the degree of doping x increased was related to the redistribution of the volumes of two phases (two types of regions) with different degrees of freedom of electron holes on manganese sites. The ferromagnet-paramagnet phase transition was a smooth redistribution of the volumes of ferromagnetic and paramagnetic (or antiferromagnetic) regions in a wide temperature range. Ferromagnetic conductivity was caused by the “double exchange” mechanism, whereas, in comparatively nonconducting regions, double exchange was considerably weakened and involved fairly slow thermally activated motion of Jahn-Teller polarons. The dynamics of nuclear spins was evidence of internal inhomogeneity of each of these phases. |
| Databáze: | OpenAIRE |
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