STRUCTURAL AND MAGNETOTRANSPORT PROPERTIES OF THE COLOSSAL MAGNETORESISTANCE MATERIAL TL2MN2O7

Citation
Y. Shimakawa et al., STRUCTURAL AND MAGNETOTRANSPORT PROPERTIES OF THE COLOSSAL MAGNETORESISTANCE MATERIAL TL2MN2O7, Physical review. B, Condensed matter, 55(10), 1997, pp. 6399-6404
Citations number
28
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
55
Issue
10
Year of publication
1997
Pages
6399 - 6404
Database
ISI
SICI code
0163-1829(1997)55:10<6399:SAMPOT>2.0.ZU;2-O
Abstract
The crystal structure and its variation with temperature of the spin-c harge coupled material Tl2Mn2O7 pyrochlore is investigated. Structure refinement from the neutron powder-diffraction data reveals that Tl2Mn 2O7 has nearly stoichiometric composition and is crystallized in the c ubic-pyrochlore-type structure with a characteristic Mn-O-Mn bond angl e of 133 degrees. There is no structural anomaly associated with the c hange in magnetotransport properties at 142 K, suggesting weak spin-la ttice and charge-lattice correlations. Despite the similarity of magne totransport properties observed in the perovskite and the pyrochlore c olossal magnetoresistance manganese oxides, the double-exchange mechan ism, which is usually applied to the perovskite materials, does not se em to explain the behavior in the pyrochlore Tl2Mn2O7 compound. A supe rexchange-type interaction may stabilize the ferromagnetic ordering of Mn spins and cause the metallic conduction at low temperatures in Tl2 Mn2O7.