Europhys. Lett.
Volume 65, Number 6, March 2004
Page(s) 823 - 829
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 March 2004
Europhys. Lett., 65 (6) , pp. 823-829 (2004)
DOI: 10.1209/epl/i2003-10198-7

Current dependence of the magnetoresistance in a colloidal-sphere-masked ion-milled $\chem{La_{0.67}Sr_{0.33}MnO_{3}}$ thin film

J. Li1, 2, D. N. Zheng1, X. S. Rao3, C. H. Sow2, L. Chen1 and C. K. Ong2

1  National Laboratory for Superconductivity, Institute of Physics Chinese Academy of Sciences - Beijing 100080, PRC
2  Centre for Superconducting and Magnetic Materials (CSMM) and Department of Physics, National University of Singapore 2 Science Drive 3, Singapore 117542
3  Temasek Laboratories, National University of Singapore Engineering Drive 3, Singapore 119260

(Received 11 August 2003; accepted in final form 8 January 2004)

An epitaxial $\chem{La_{0.67}Sr_{0.33}MnO_{3}}$ thin film covered with a monolayer of colloidal spheres was ion-milled so that structural discontinuities were involved. Nonlinear V- I characteristics have been observed, revealing that the zero-field resistance of the sample decreases with increasing measuring current I. In a magnetic field, however, the resistance varies non-monotonically with I. An inflexion appears around I=50 $\un{nA}$. Accordingly, the magnetoresistance also correlates with I. A maximum value as high as $-700\%$ ( $\Delta R/R_{H}$) is recorded at liquid nitrogen in 1.5 $\un{T}$ when I=1 $\un{nA}$. The drastic current dependence of the magnetoresistance is believed to come from the ion-milling-induced structural and magnetic disorders and to be related to the inelastic scattering of the spin-polarized electrons at the disorders. The possible underlying mechanisms are discussed in detail.

75.47.Gk - Colossal magnetoresistance.
75.47.Lx - Manganites.
72.25.Dc - Spin polarized transport in semiconductors.

© EDP Sciences 2004