Volume 45, Number 3, February 1999
|Page(s)||399 - 405|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
Transition from itinerant to polaronic conduction in perovskites
Istituto Nazionale per la Fisica della Materia and
Università di Ancona Via Brecce Bianche, 60131 Ancona, Italy
2 Departamento de Física Aplicada, Universidade de Santiago E-15706 Santiago de Compostela, Spain
3 Departamento Quimica Fundamental e Industrial, Universidade da Coruña 15071 A Coruña, Spain
4 Rutherford Appleton Laboratory, ISIS Facility - Chilton, UK
5 Institut für Festkörperforschung des Forschungszentrum - 52425 Jülich, Germany
6 Istituto di Chimica dei Materiali, CNR - 00016 Monterotondo, Roma, Italy
7 Center for Materials Science and Engineering, University of Texas at Austin Texas 78712-1063, USA
Accepted: 23 November 1998
Neutron diffraction and small-angle scattering on () show that for x = 0.3 the system is near a two-phase percolation threshold and undergoes a transition from itinerant to polaronic conduction at the Curie temperature TC. The stabilization of superparamagnetic clusters on warming through TC is revealed by an anomalous thermal expansion of the volume and a deviation of the paramagnetic susceptibility from the Curie-Weiss law. The development of a temperature-dependent small-angle-scattering signal confirms that regions of short-range ferromagnetic order are present above .
PACS: 75.25.+z – Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.) / 72.15.-v – Electronic conduction in metals and alloys / 75.40.Cx – Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
© EDP Sciences, 1999
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