Partially crystallized La0.5Sr0.5MnO3 thin films by laser ablation and their enhanced low-field magnetoresistance

Amorphous, partial-crystallized, and epitaxial La0.5Sr0.5MnO3 thin films have been deposited at various temperatures of 200-650 degrees C on (001) SrTiO3 substrates using pulsed-laser deposition. The x-ray diffraction and high-resolution transmission electron microscopy indicate complete (001) orientation of the crystalline structures in these films. Enhanced low-field magnetoresistance effect has been observed for the partial-crystallized thin films where the nanosized ferromagnetic crystals are embedded in nonferromagnetic amorphous matrix. It is argued that the amorphous layer separating the neighboring nanocrystals behaves as the barrier for the spin-polarized tunneling and/or spin-dependent scattering, resulting in enhanced magnetoresistance at low magnetic field. (C) 2000 American Institute of Physics. [S0003-6951(00)05316-X].