MAGNETIC, ELECTRICAL, AND CRYSTALLOGRAPHIC PROPERTIES OF THIN LA1-XSRXMNO3 FILMS

A study is reported of the magnetic, electrical, and crystallographic properties of La1-xSrxMnO3 (0.15 less than or equal to x less than or equal to 0.23) epitaxial films grown on single-crystal substrates of ( 001)ZrO2(Y2O3) having the fluorite structure and (001)LaAlO3 having th e perovskite structure. It was found that films with close composition s for x=0.15 and 0.16, grown on different substrates, have different p roperties, namely, the film on a fluorite substrate is semiconducting and has a coercive strength 30 times that of the film on a perovskite substrate; the temperature dependence of electrical resistance of the latter film has a maximum around the Curie point T-C and follows metal lic behavior for T<T-C. These differences are explained as due to diff erent structures of the films. The x=0.23 film on the perovskite subst rate has been found to exhibit a combination of giant magnetoresistanc e at room temperature with a resistance of approximate to 300 Ohm whic h is useful for applications. The maxima in resistance and absolute va lue of negative magnetoresistance are accounted for by the existence o f two-phase magnetic states in these films. (C) 1998 American Institut e of Physics.