Low field magnetoresistance in bicrystalline manganite films: dependence with angle

G. ALEJANDRO; H. PASTORIZA; M. GRANADA; D. VEGA; L. B. STEREN; B. ALASCIO

Villigen, Suiza

Workshop; International Workshop on X-ray Spectroscopy; 2005

The ferromagnetic manganites, in addition to the colossal magnetoresistance (CMR) near the Curie point, exhibit at low temperatures an extrinsic low field magnetoresistance (LFMR) that arises from scattering at the grain boundaries. The choice of studying manganite films deposited on bicrystalline substrates has the main advantage of isolating a unique artificial grain boundary (AGB). Recently, noticeable differences between the LFMR curves measured with the magnetic field parallel and perpendicular to the AGB have been published. Here we report on LFMR measurements performed on La0.75Sr0.25MnO3 films sputtered on SrTiO3 bicrystalline substrates. A Wheatstone bridge of micrometric track width was patterned by electron lithography, and the angular variation of the LFMR was investigated by recording the resistivity of the film at several different angles between the AGB and the magnetic field.  We have observed that the field dependence of the LFMR strongly varies with this angle, though the LFMR magnitude remains almost constant. X-ray diffraction measurements, ferromagnetic resonance (FMR), and dc-magnetization experiments complement this study.