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Coupling of Small Lattice Polarons to Magnetic Field in Magnetoresistive Manganites
Author(s) -
Meneghini C.,
Castellano C.,
Kumar Ashwani,
Ray Sugata,
Sarma D. D.,
Mobilio S.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199909)215:1<647::aid-pssb647>3.0.co;2-0
Subject(s) - polaron , condensed matter physics , magnetoresistance , materials science , manganite , magnetic field , colossal magnetoresistance , manganese , ferromagnetism , physics , electron , quantum mechanics , metallurgy
We report Extended X‐Ray Absorption Fine Structure measurements at the Mn K absorption edge on hole doped manganese oxides La 1— x Ca x MnO 3 in a wide temperature range above and below the metal–insulator transition temperature in presence of a magnetic field. In accordance with previous studies an anomalous increase in the Debye‐Waller factors is detected at the phase transition in the first coordination shell made up of O atoms. This is due to a local structural deformation around Mn 3+ atoms associated with the Jahn‐Teller effect and the formation of polarons. The application of a magnetic field results in a variation of this deformation with a thermal behaviour that closely resembles that of the magnetoresistance. This confirms the relevance of the polarons on the conductivity properties of such materials. The magnetic field has a huge effect on the second coordination shell probably related with the change of the Mn–O–Mn angle upon application of the magnetic field.