ANISOTROPIC PROPERTIES OF MOLECULAR-BEAM EPITAXY-GROWN COLOSSAL MAGNETORESISTANCE MANGANITE THIN-FILMS

We show that both the magnetoresistance and magnetism in tetragonal MB E-grown films of La1-xCaxMnO3 show anisotropic effects that depend on both temperature and magnetic field. We show that the ''colossal'' mag netoresistance depends on the angle between the magnetization and the transport current and that the size of this effect is temperature-depe ndent. Below the Curie temperature this results in an unusual upturn i n the magnetoresistance for small magnetic fields normal to the plane of the film as the magnetization rotates out of the plane. Low-field h ysteresis of the in-plane magnetoresistance is also observed, and also shows an anisotropy with respect to the current and magnetization dir ections. We also find an in-plane biaxial magnetocrystalline anisotrop y with easy axes along the {100} (Mn-O) crystal directions, and eviden ce for c-axis magnetocrystalline anisotropy. (C) 1997 American Institu te of Physics.