THICKNESS DEPENDENCE OF MAGNETORESISTANCE IN LA-CA-MN-O EPITAXIAL-FILMS

Colossal magnetoresistance in excess of 10(6)% has been obtained (at 1 10 K, H=6 T) in epitaxially grown La-Ca-Mn-O thin films. The as-deposi ted film exhibits a substantial magnetoresistance value of 39 000%, wh ich is further improved by heat treatment. The magnetoresistance is fo und to be strongly dependent on film thickness, with the value reachin g the maxima at similar to 1000 Angstrom thickness, and then reduced b y orders of magnitude when the film is made thicker than similar to 20 00 Angstrom. This behavior is interpreted in terms of lattice strain i n the La-Ca-Mn-O films. (C) 1995 American Institute of Physics.