Current dependence of the magnetoresistance in a colloidal-sphere-masked ion-milled La 0.67Sr 0.33MnO 3 thin film

Abstract

An epitaxial La 0.67Sr 0.33MnO 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 nA. Accordingly, the magnetoresistance also correlates with I. A maximum value as high as -700% (ΔR/R H) is recorded at liquid nitrogen in 1.5 T when I = 1nA. 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.