Materials aspects of laser-ablation-deposited cuprate/manganate bilayers for spin-polarized injection devices

We report studies of cuprate/manganate bilayers deposited onto SrTiO3 substrates by laser ablation. A significant difference in the properties of the individual layers is observed depending on the material deposition sequence. The material which is on the bottom of the multilayer shows worse properties, e.g., a critical temperature of similar to 60 K for YBa2Cu3O7-delta (YBCO) covered by La2/3Ca1/3MnO3 (LCMO) as opposed to a value of similar to 90 K when YBCO is on the top. Similarly, the LCMO film has its metal-insulator transition temperature shifted below the Curie temperature when the YBCO is on top. We argue that the effect is not due to degraded crystal quality, cation substitution, or an electronic interaction, but results from a reduction in the oxygen content of the underlying layer. We find that this reduction is a feature of the complete LCMO layer and is not associated with the constituent elements. We discuss possible explanations for this effect. (c) 2005 American Institute of Physics.