Colossal Magnetoresistance in thin films of the Mott metal CaVO$_{3 }$

Bulk CaVO$_{3}$ (CVO) is a Pauli paramagnetic metal with a singe 3d electron. Some unusual drastic changes in the magneto-resistance, magnetic susceptibility and the Hall effect have been reported in single crystal CVO. We have simultaneously synthesized epitaxial CVO films grown on three differently oriented SrTiO$_{3}$ substrates. The temperature dependent conductivity of these CVO films demonstrated very strong Fermi metal behavior and the resistance ratio, defined as R(300 K)/R (2K) was more than 3000. Colossal magneto-resistance (MR) as well as large crystalline anisotropic was observed at low temperatures. The maximum MR, defined as (R(7 T)-R(0 T))/R(0 T)*100 {\%}, was over 1500 {\%} at 2 K and 7 Telsa on the CVO films deposited on a (110) SrTiO3 single crystal substrate, and didn't show any sign of saturation. An MR of over $\sim $ 500 {\%} and $\sim $ 200 {\%} were observed on (111) and (100) orientation films under the same condition, respectively. The MR ratio was much larger than that of single crystal CVO. We will discuss the peculiar MR in association with the magnetic ordering, oxygen stoichiometry and Fermi surface.