arXiv subjects

Carlos León

Publications and source records attributed to Carlos León.

3 recordsLinked to original sources

arXiv2026

Emergent exchange bias in ultra-thin La0.67Sr0.33MnO3 films driven by ferro-antiferromagnetic phase coexistence

Ultra-thin La0.67Sr0.33MnO3 (LSMO) films are generally regarded as single-phase ferromagnets, yet their reduced dimensionality enhances the impact of oxygen stoichiometry and local structural distortions. Here we demonstrate that LSMO layers with thicknesses between 3 and 17 nm develop a robust and thickness-independent exchange bias (EB) despite the absence of an engineered ferromagnetic-antiferromagnetic (FM-AFM) interface. Angular magneto-optical Kerr effect measurements reveal a reproducible hysteresis-loop shift that reverses sign upon 180-degree rotation, confirming its intrinsic origin. X-ray photoelectron spectroscopy shows a thickness-independent Mn2+ fraction (about 20 percent), indicating the presence of oxygen-deficient reduced regions embedded within the Mn3+/Mn4+ ferromagnetic matrix. A simple interfacial-exchange model suggests that only a sub-percent fraction of antiferromagnetic (or frustrated spin-ice-like) regions is required to generate the observed EB. These results demonstrate that ultra-thin LSMO can spontaneously host internal FM-AFM interfaces driven by oxygen deficiency, revealing an emergent route to exchange bias in nominally single-phase manganite films.

cond-mat.mtrl-sci↗

arXiv2017

Photodiodes based in La0.7Sr0.3MnO3/single layer MoS2 hybrid vertical heterostructures

The fabrication of artificial materials by stacking of individual two-dimensional (2D) materials is amongst one of the most promising research avenues in the field of 2D materials. Moreover, this strategy to fabricate new man-made materials can be further extended by fabricating hybrid stacks between 2D materials and other functional materials with different dimensionality making the potential number of combinations almost infinite. Among all these possible combinations, mixing 2D materials with transition metal oxides can result especially useful because of the large amount of interesting physical phenomena displayed separately by these two material families. We present a hybrid device based on the stacking of a single layer MoS2 onto a lanthanum strontium manganite (La0.7Sr0.3MnO3) thin film, creating an atomically thin device. It shows a rectifying electrical transport with a ratio of 103, and a photovoltaic effect with Voc up to 0.4 V. The photodiode behaviour arises as a consequence of the different doping character of these two materials. This result paves the way towards combining the efforts of these two large materials science communities.

cond-mat.mes-hall↗

arXiv2014

Competition between covalent bonding and charge transfer at complex-oxide interfaces

Here we study the electronic properties of cuprate/manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high $T_c$ superconductor YBa$_2$Cu$_3$O$_{7-δ}$ and the colossal magnetoresistance compound (La,Ca)MnO$_3$. A net transfer of electrons from manganite to cuprate with a peculiar non-monotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales.

cond-mat.mtrl-sci↗