Strain Effect of La_<n-nx>Ca_<1+nx>Mn_nO_<3n+1> Thin Films  [in Japanese]

The electrical and magnetic properties, including the magnetoresistance (MR) effect, of La_<n-nx>Ca_<1+nx>Mn_nO_<3n+1> thin films (n=∞, 2; x=0.3) grown on various substrates were investigated. For n=2 (La_<1.4>Ca_<1.6>Mn_2O_7) thin films, the cusp temperature (T_c^^ρ) in the p-T curve decreased very sharply with a decrease of the out-of-plane lattice parameter (a). The MR effect was enhanced drastically by decreasing T_c^^ρ. These behavilrs are interpreted in relation to the change in the transport character along the c-axis due to the strain.