Europhys. Lett, 47 (3), pp. 371-377 (1999)
On the nature of grain boundaries in the colossal magnetoresistance manganites
J. Klein, C. Höfener, S. Uhlenbruck, L. Alff, B. Büchner and R. Gross
II. Physikalisches Institut, Universität zu Köln
Zülpicherstr. 77, D-50937 Köln, Germany
(received 23 March 1999; accepted in final form 1 June 1999)
PACS. 75.30Vn - Colossal magnetoresistance.
PACS. 73.40 - Electronic transport in interface structures.
PACS. 75.70Cn - Interfacial magnetic properties (multilayers, magnetic quantum wells, superlattices, magnetic heterostructures).
The electrical transport properties of grain boundaries in the epitaxial
thin films have been studied as a function of temperature and applied magnetic field. Below the Curie temperature an additional grain boundary resistance, highly non-linear current-voltage curves, and a large magnetoresistive effect in the whole temperature regime below are found. The results can be explained consistently by the presence of a disordered, a few nm wide paramagnetic grain boundary layer that is depleted below due to an increase of the work function of the ferromagnetic grain material adjacent to this layer. The related band bending and space charge effects are important for the physics of grain boundaries in the manganites.
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