Large magnetoresistance effect in as-grown epitaxial LaxCa1-xMnO3 films prepared by a molecular beam epitaxy coevaporation technique

• Thin films of LaxCa1-xMnO3 (0.64 less than or equal to x less than or equal to 0.68) have been grown by NO2-assisted molecular beam epitaxy on single crystal SrTiO3(100) and LaAlO3(100) substrates. As-grown films are found to be grown epitaxially, b-axis oriented on both SrTiO3 and LaAlO3 substrates, and exhibit a large magnetoresistance effect {[R(O)-R(H)]/R(H)X100} of about 1500% at 214 K. The magnetoresistance effect values obtained are similar to those reported for as-grown LaxCa1-xMnO3 (0.60 less than or equal to x less than or equal to 0.7) films synthesized either by so-called "block-by-block" or "layer-by-layer" molecular beam epitaxy techniques, but the effect appears at significantly higher temperatures. For epitaxial La0.68Ca0.32MnO3 films grown on SrTiO3 a relatively large resistance suppression of 200% at 1.0 T is observed. (C) 1998 American Vacuum Society.

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