ENHANCED FIELD SENSITIVITY IN THE TRANSVERSE MAGNETORESISTANCE OF THIN EPITAXIAL-FILMS OF LA0.66CA0.34MNO3

We investigated the transverse resistance as a function of temperature and magnetic field in thin epitaxial films of La0.66Ca0.34MnO3 patter ned in a Hall-effect configuration. The transverse resistance shows a sharp peak just below the magnetic phase transition, which is present in zero applied magnetic field, does not change sign as the applied ma gnetic field is reversed, and therefore is not a Hall effect. The tran sverse peak is much more sensitive than the longitudinal magnetoresist ance: it changes by 10% in small applied fields of the order of 100 G. We suggest that this may be caused by an inhomogeneous distribution o f resistances and Curie temperatures within the film. With this in min d, we have carried out simulations using a two-dimensional resistor ne twork that reproduce the key features of this novel effect, as well as the rounding of the longitudinal resistance and the broadening of the magnetization.