Transport and magnetic properties of laser ablated La0.7Ce0.3MnO3 films onLaAlO3

La0.7Ce0.3MnO3 is a relatively new addition to the family of colossal magne toresistive manganites, in which the cerium ion is believed to be in the Ce 4+ state. In this article, we report the magnetotransport properties of las er ablated La0.7Ce0.3MnO3 films on LaAlO3, and the effect of varying the am bient oxygen pressure during growth and the film thickness. We observe that the transport and magnetic properties of the film depend on the oxygen pre ssure, surface morphology, film thickness, and epitaxial strain. The films were characterized by x-ray diffraction using a four-circle goniometer. We observe an increase in the metal-insulator transition temperature with decr easing oxygen pressure. This is in direct contrast to the oxygen pressure d ependence of La0.7Ca0.3MnO3 films and suggests the electron doped nature of the La0.7Ce0.3MnO3 system. With decreasing film thickness we observe an in crease in the metal-insulator transition temperature. This is associated wi th a compression of the unit cell in the a-b plane due to epitaxial strain. On codoping with 50% Ca at the Ce site, the system (La0.7Ca0.15Ce0.15MnO3) is driven into an insulating state suggesting that the electrons generated by Ce4+ are compensated by the holes generated by Ca2+, thus making the av erage valence at the rare-earth site 3+ as in the parent material LaMnO3. ( C) 1999 American Institute of Physics. [S0021-8979(99)03522-7].