High-TC ferromagnetic order in CaRuO3/La2/3Ca1/3MnO3 superlattices

摘要

Ferromagnetic-metallic ground state with high Curie temperature (TC) of 200–258 K has been observed in CaRuO3/La2/3Ca1/3MnO3 (CRO/LCMO) superlattices with the ultrathin LCMO layer of 0.8–3.2 nm thick. This contradicts the antiferromagnetic or low-TC insulating ground state observed in single-layer LCMO thin-films. TC and the saturated magnetization of the superlattices are determined dominantly by the LCMO layer thicknesses, indicating no direct magnetic contribution from the CRO layers or the interfaces. Also, they are less sensitive to the growth oxygen pressure as compared to the pure LCMO films. We ascribe the stabilized, bulklike ferromagnetism in the ultrathin LCMO layer to charge transfer from CRO at the interfaces, which could enhance the double-exchange and meanwhile suppress the phase separation, contrary to the case for LCMO thin-films. This interface engineering that can greatly depress the notorious “dead layer” in manganites might be significant in designing the correlated spintronic devices.