Volume 58, Number 2, April 2002
|Page(s)||285 - 291|
|Section||Condensed matter: electronic structure, electrical, magnetic, and optical properties|
|Published online||01 August 2002|
Spin-dependent hopping in the paramagnetic state of the bilayer manganite
Laboratorium voor Vaste-Stoffysica en Magnetisme,
Katholieke Universiteit Leuven Celestijnenlaan 200 D,
B-3001 Leuven, Belgium
2 Laboratoire de Physico-Chimie de l'Etat Solide, UMR 8648 Bâtiment 414, Université Paris-Sud, F-91405 Orsay, France
Corresponding author: Ivan.Gordon@fys.kuleuven.ac.be
Accepted: 25 January 2002
We report on the scaling behaviour of the colossal negative magnetoresistance effect (CMR) in a single crystal of the bilayer manganite . The high content is responsible for the absence of long-range ferromagnetism and for a CMR effect in the order of 106. The system is down to the Neél temperature ( ) in a superparamagnetic state with spin clusters extending over 6–9 unit cells. The coefficient C, which describes the magnetization-induced resistance drop in the paramagnetic state, has absolute values up to C= 15 at 100. The temperature dependence is explained by spin-dependent hopping between magnetic clusters. Spin-dependent scattering and Kondo-lattice models do not account for the magnitude of C and its variation with temperature.
PACS: 75.30.Vn – Colossal magnetoresistance / 72.20.Ee – Mobility edges; hopping transport / 75.20.-g – Diamagnetism, paramagnetism, and superparamagnetism
© EDP Sciences, 2002
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