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Colossal magnetoresistance; bicrystal junction; grain boundary; LBMO; spin-polarized tunneling

La_0.67Ba_0.33MnO₃ (LBMO) thin film is deposited on a 36.7°C SrTiO₃ bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance with the increase in temperature is due to enhanced spin-flip scattering process.

Neeraj Khare¹ AK Gupta¹ UP Moharil¹ AK Raychaudhuri² SP Pai³ R Pinto³

1. National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi - 110 012, India
2. Indian Institute of Science, Bangalore - 560 012, India
3. Tata Institute of Fundamental Research, Colaba, Mumbai - 400 005, India

Published

6 May 2002