Mechanical and liquid phase exfoliation of cylindrite: A natural van der Waals superlattice with intrinsic magnetic interactions

We report the isolation of thin flakes of cylindrite, a naturally occurring van der Waals superlattice, by means of mechanical and liquid phase exfoliation. We find that this material is a heavily doped p-Type semiconductor with a narrow gap (<0.85 eV) with intrinsic magnetic interactions that are preserved even in the exfoliated nanosheets. Due to its environmental stability and high electrical conductivity, cylindrite can be an interesting alternative to the existing 2D magnetic materials

Reversible electric-field control of magnetization at oxide interfaces

Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field

Formation of titanium monoxide (001) single-crystalline thin film induced by ion bombardment of titanium dioxide (110)

A plethora of technological applications justify why titanium dioxide is probably the most studied oxide, and an optimal exploitation of its properties quite frequently requires a controlled modification of the surface. Low-energy ion bombardment is one of the most extended techniques for this purpose and has been recently used in titanium oxides, among other applications, to favour resistive switching mechanisms or to form transparent conductive layers. Surfaces modified in this way are frequently described as reduced and defective, with a high density of oxygen vacancies. Here we show, at variance with this view, that high ion doses on rutile titanium dioxide (110) induce its transformation into a nanometric and single-crystalline titanium monoxide (001) thin film with rocksalt structure. The discovery of this ability may pave the way to new technical applications of ion bombardment not previously reported, which can be used to fabricate heterostructures and interfaces

Atomic resolution STEM-EELS studies of defects and local structural distortions in oxide interfaces

Doped complex oxides show a wide range of interesting properties due to a strong interplay andcompetition between lattice, spin, and charge degrees of freedom. In these systems, subtle changes inlocal structure or chemistry may result in colossal responses in macroscopic physical behavior. In thistalk we will apply atomic resolution aberration corrected scanning transmission electron microscopy(STEM) and electron energy-loss spectroscopy (EELS) to the study of the chemistry and local structurearound defects, near complex oxide interfaces, and grain boundaries. Thanks to spherical aberrationcorrection, both spatial resolution and sensitivity limits attainable in the STEM have improved down tothe single-atom level, resulting in unprecedented contrast and signal-to-noise ratio improvements in both imaging and EELS. We will discuss a few examples where atomic resolution compositional mapping constitutes a key task to understand the system physical properties, highlighting the importance of considering artifacts during quantification.Fil: Sánchez Santolino, G.. University of Tokyo; JapónFil: Roldan, M. A.. Universidad Complutense de Madrid; EspañaFil: Qiao, Qiao. Temple University; Estados Unidos. Brookhaven National Laboratory; Estados UnidosFil: Begon Lours, L.. Centre National de la Recherche Scientifique; FranciaFil: Frechero, Marisa Alejandra. Universidad Complutense de Madrid; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Salafranca, J.. Universidad Complutense de Madrid; EspañaFil: Mishra, R.. Washington University in St. Louis; Estados UnidosFil: Leon, C.. Universidad Complutense de Madrid; EspañaFil: Pantelides, S. T.. Vanderbilt University; Estados UnidosFil: Pennycook, S. J.. National University of Singapore; SingapurFil: Villegas, J. E.. Centre National de la Recherche Scientifique; FranciaFil: Santamaria, J.. Universidad Complutense de Madrid; EspañaFil: Varela, M.. Universidad Complutense de Madrid; Españ