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Inverse TMR Effect in Co0.9Fe0.1/SrTiO3/La0.7Sr0.3MnO3 Tunnel Junctions

Published online by Cambridge University Press:  17 March 2011

M. Sugiyama
Affiliation:
Dept. of Crystalline Materials Science, Nagoya Univ., Nagoya, 464-8603, Japan
H. Asano
Affiliation:
Dept. of Crystalline Materials Science, Nagoya Univ., Nagoya, 464-8603, Japan
M. Matsui
Affiliation:
Dept. of Crystalline Materials Science, Nagoya Univ., Nagoya, 464-8603, Japan
J. Hayakawa
Affiliation:
Hitachi Ltd., Central Research Laboratory, Kokubunji, 185-8601, Japan
S. Kokado
Affiliation:
Hitachi Ltd., Central Research Laboratory, Kokubunji, 185-8601, Japan
K. Itou
Affiliation:
Hitachi Ltd., Central Research Laboratory, Kokubunji, 185-8601, Japan
A. Sakuma
Affiliation:
Hitachi Metals Ltd., Kumagaya, 360-0843, Japan
M. Ichimura
Affiliation:
Hitachi Ltd., Advanced Research Laboratory, Akanuma, 350-0395, Japan
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Abstract

Magnetic tunnel junctions of Co0.9Fe0.1/SrTiO3 (STO)/ La0.7Sr0.3MnO3 (LSMO) with a spin-valve structure having an antiferromagnetic MnIr layer have been fabricated by sputtering. Junction magnetoresistance (MR) behavior and its dependence on the bias voltage are examined for junctions with epitaxial STO barrier formed under different sputtering conditions. Spin dependent transport measurements show that these junctions exhibit spin-valve type MR loops with an inverse (positive) MR of the ratio of 14-22 % at 4.2 K. The inverse MR observed is asymmetric with respect to the bias voltage direction. Stoichiometric STO barrier, as characterized by Rutherford backscattering (RBS) analysis, is found to result in very large asymmetric bias dependence, while the junctions with nonstoichiometric STO barrier exhibit the symmetric bias dependence. Our results suggest that the nonstoichiometry of STO barrier modifies the electronic structures of electrode/barrier interfaces, and thereby reducing the asymmetry of bias voltage dependence of junction MR.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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References

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