Hall effect and giant magnetoresistance in lanthanum manganite thin films

Magnetoresistance and Hall coefficient have been investigated as a function of temperature in patterned thin films of La-Ca-Mn-O. Our data on magnetoresistance show a maximum magnetoresistance ratio Delta rho/rho(O) of approximate to-60% at 1.5 T and 240 K. The Hall coefficient indicates that the carriers are predominantly holes, with apparent density that varies as a function of temperature. Although changes in mobility were also observed, our results indicate that changes in carrier density become more important than changes in mobility at temperatures lower than the Curie temperature. We interpret our data in terms of a simple picture that includes two parallel contributions to the carrier density and the conductivity. (C) 1996 American Institute of Physics.