Anisotropic properties of molecular beam epitaxy-grown colossal magnetoresistance manganite thin films

We show that both the magnetoresistance and magnetism in tetragonal MBE-grown films of La1-xCaxMnO3 show anisotropic effects that depend on both temperature and magnetic field. We show that the ''colossal'' magnetoresistance depends on the angle between the magnetization and the transport current and that the size of this effect is temperature-dependent. Below the Curie temperature this results in an unusual upturn in the magnetoresistance for small magnetic fields normal to the plane of the film as the magnetization rotates out of the plane. Low-field hysteresis of the in-plane magnetoresistance is also observed, and also shows an anisotropy with respect to the current and magnetization directions. We also find an in-plane biaxial magnetocrystalline anisotropy with easy axes along the {100} (Mn-O) crystal directions, and evidence for c-axis magnetocrystalline anisotropy. (C) 1997 American Institute of Physics.