C. Hofener et al., Voltage and temperature dependence of the grain boundary tunneling magnetoresistance in manganites, EUROPH LETT, 50(5), 2000, pp. 681-687
We have performed a systematic analysis of time voltage and temperature dep
endence of the tunneling magnetoresistance (TMR) of grain boundaries (GB) i
n the manganites. We find a strong decrease of the TMR with increasing volt
age and temperature. The decrease of the TMR with increasing voltage scales
with an increase of time inelastic tunneling current due to multi-step ine
lastic tunneling via localized defect, states in the tunneling barrier. Thi
s behavior can be described, within a three-current model for magnetic tunn
el junctions that extends thc two-current Julliere model by adding an inela
stic, spin-independent tunneling contribution. Our analysis gives strong ev
idence that the observed drastic decrease of the GB-TMR in manganites is ca
used by an imperfect tunneling barrier.