Phase Separation at Interfaces in La2/3Ca1/3MnO3 Thin Films

Abstract

ABSTRACTWe present an extensive physical characterization of La2/3Ca1/3MnO3 (LCMO) epitaxial films grown on SrTiO3 (STO), LaAlO3 (LAO) and NdGaO3 (NGO) substrates. The main difference among these substrates is that they have a different mismatch (∼ 1.2%, -1.8% and - 0.1%, respectively) with the manganite. The films can be coherently grown up to 180 nm for STO and NGO but partial relaxation is observed for LAO. The magnetotransport data indicate that very thin films (<27nm) display non-conventional magnetoresistive properties: a substantial magnetoresistance develops which can be progressively appreciated for STO and LAO films. 55Mn-Nuclear Magnetic Resonance experiments on all these films reveal the presence of non-homogeneous electronic states. These experiments in fact provide clear evidence of the presence of two distinguishable ferromagnetic Mn states and a non-ferromagnetic phase. The possible role of strain-induced charge localization is discussed. It turns out that electronic phase separation occurs in all films irrespectively of the particular substrate used; thus we conclude that strain is not the unique driving force for charge localization.