Anisotropic electrical transport in epitaxial La2/3Ca1/3MnO3 thin films

Epitaxial thin films of La0.62 +/- 0.05Ca0.33 +/- 0.02MnO3-delta were grown by laser ablation on SrTiO3. On (100) substrates the films grow with the larger c axis perpendicular to the plane. The films deposited on (110) SrTiO3 grow with both the c (long) axis and a (or b, short) axis in the plane of the film. The electrical resistivity (rho) and the magnetoresistance (Delta rho/rho) show crystalline anisotropy. The resistivity ratio between the a and c axis is constant (0.8) from 10 K up to 120 K and decreases to 0.77 between 125 and 225 K, shows a small peak anomaly at T-c (257 K), and is almost constant in the paramagnetic phase. This temperature dependence is associated with anisotropic local lattice distortions. The magnetoresistance anisotropy (Delta rho/rho(parallel to)-Delta rho/rho(perpendicular to)) with the applied field in the plane of the film, is small at low temperatures, peaks close to T-c, and is slightly larger for measurements along the a axis. The contributions of domain rotation and magnetocrystalline anisotropy to the anisotropic magnetoresistance associated with spin-orbit coupling are discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)55108-1].