Europhys. Lett., 50 (5), p. 681 (2000)

Voltage and temperature dependence of the grain
boundary tunneling magnetoresistance in manganites

C. Höfener - J. B. Philipp - J. Klein - L. Alff - A. Marx -
B. Büchner - R. Gross

II. Physikalisches Institut, Universität zu Köln
Zülpicher Str. 77, D-50937 Köln, Germany

PACS :
75.70.Cn - Interfacial magnetic properties (multilayers, magnetic quantum wells, superlattices, magnetic heterostructures)
75.70.Ak - Magnetic properties of monolayers and thin films
73.40.-c - Electronic transport in interface structures

gross@ph2.uni-koeln.de

Abstract:

We have performed a systematic analysis of the voltage and temperature dependence of the tunneling magnetoresistance (TMR) of grain boundaries (GB) in the manganites. We find a strong decrease of the TMR with increasing voltage and temperature. The decrease of the TMR with increasing voltage scales with an increase of the inelastic tunneling current due to multi-step inelastic tunneling via localized defect states in the tunneling barrier. This behavior can be described within a three-current model for magnetic tunnel junctions that extends the two-current Jullière model by adding an inelastic, spin-independent tunneling contribution. Our analysis gives strong evidence that the observed drastic decrease of the GB-TMR in manganites is caused by an imperfect tunneling barrier.

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