MAGNETORESISTANCE SCALING IN MBE-GROWN LA0.7CA0.3MNO3 THIN-FILMS

We present a detailed analysis of magnetoresistance in tetragonal thin films of ferromagnetic La0.7Ca0.3MnOdelta grown by atomic layer-by-la yer molecular-beam epitaxy. The field and temperature dependence of th e resistivity rho show an explicit dependence only on the fractional m agnetization M/M(sat) and are consistent with a single approximate for m rho approximate to rho(0)exp[-C(M/M(sat))(2)] for small and intermed iate magnetization both above and below the Curie temperature (T-C) Th e microscopic magnetization and susceptibility (chi) have been inferre d from the low-field magnetoresistance above T-C with chi following a Curie-Weiss form. We:observe a sharp transition in the low-held (H) de pendence of rho from quadratic (proportional to H-2) above T-C to line ar (proportional to H) below, consistent with a temperature-independen t rho(M). Finally we show that within a simple model this temperature- independent form for rho reproduces the behavior of the measured low-f ield sensitivity below T-C.