Long-range electronic reconstruction to a dxz,yz-dominated Fermi surface below the LaAlO3/SrTiO3 interface

Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial ‘‘depth’’ - remains unclear. Examining LaAlO3/SrTiO3 heterostructures at previously unexplored carrier densities n2D 14 cm-2 , we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential dxz,yz orbital occupancy extending over at least 100 nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO3 emerge simultaneously at higher n2D. We distinguish three areas in doped perovskite heterostructures: narrow (nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (\u3e120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk

Emergent vortices at a ferromagnetic superconducting oxide interface

Understanding the cohabitation arrangements of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface remains an open challenge. Probing this coexistence with sub-Kelvin magnetotransport experiments, we demonstrate that a hysteretic in-plane magnetoresistance develops below the superconducting transition for H \u3c 0.15 T, independently of the carrier density or oxygen annealing. This hysteresis is argued to arise from vortex depinning within a thin (\u3c 20 nm) superconducting layer, mediated by discrete ferromagnetic dipoles located solely above the layer. The pinning strength may be modified by varying the superconducting channel thickness via electric field-effect doping. No evidence is found for bulk magnetism or finite-momentum pairing, and we conclude that ferromagnetism is strictly confined to the interface, where it competes with superconductivity. Our work indicates that oxide interfaces are ideal candidate materials for the growth and analysis of nanoscale superconductor/ferromagnet hybrids

A composite element bit design for magnetically encoded microcarriers for future combinatorial chemistry applications

We present a new composite element (CE) bit design for the magnetic bit encoding of suspended microcarriers, which has significant implications for library generation applications based on microfluidic combinatorial chemistry. The CE bit design consists of high aspect ratio strips with appropriate dipolar interactions that enable a large coercivity range and the formation of up to 14 individually addressable bits (16 384 codes) with high encoding reliability. We investigate Ni80Fe20 and Co CEs, which produce coercivity ranges of 8–290 Oe and 75–172 Oe, respectively, showing significant improvements to previously proposed bit designs. By maintaining the total magnetic volume for each CE bit, the barcode design enables a consistent stray field for in-flow magnetic read-out. The CE bit design is characterised using magneto-optic Kerr effect (MOKE) measurements and the reliability of the design is demonstrated in a multi-bit encoding process capable of identifying each bit transition for every applied magnetic field pulse. By constraining each magnetic bit to have a unique switching field using the CE design, we enable sequential encoding of the barcode using external magnetic field pulses. We therefore discuss how the new CE barcode design makes magnetically encoded microcarriers more relevant for rapid and non-invasive detection, identification and sorting of compounds in biomolecular libraries, where each microcarrier is for example capable of recording its reaction history in daisy-chained microfluidic split-and-mix processes