Contrasting size-scaling behavior of ferromagnetism in La0.67Ca0.33MnO3 films and La0.67Ca0.33MnO3/CaRuO3 multilayers

Abstract

Using La0.67Ca0.33MnO3 (LCMO) and CaRuO3 (CRO) as components, the single-layer films, bilayers, trilayers, and superlattices were fabricated on NdGaO3 (110) substrates. These epitaxial structures show quite different Curie temperature (TC) depending on the LCMO layer thickness (x), especially in the low x region. For LCMO films, TC dramatically decreases with x and disappears below 3.2 nm, as previously reported. For LCMO/CRO (CRO/LCMO) bilayers, however, a smooth decline of TC was observed, retaining a TC near 50 K at 1.6 nm. More strikingly, for the multilayers with LCMO sandwiched between CRO, TC is stabilized at ∼250 K even at x of 1.6 nm, before decreasing to 200 K at 0.8 nm. We ascribed these distinct behaviors to the LCMO/CRO interfaces, and a possible charge transfer from CRO to LCMO was suggested to play a vital role in stabilizing the ferromagnetism in ultrathin LCMO. This finding would shed some lights on the dead layer formation in ultrathin manganites and be significant in improving the performance of the related spintronic devices.