Emil Tafra

High mobility in LaAlO3/SrTiO3 heterostructures: origin, dimensionality, and perspectives.

We have investigated the dimensionality and origin of the magnetotransport properties of LaAlO3 films epitaxially grown on TiO2-terminated SrTiO3(001) substrates. High-mobility conduction is observed at low deposition oxygen pressures (P(O2)<10(-5) mbar) and has a three-dimensional character. However, at higher P(O2) the conduction is dramatically suppressed and nonmetallic behavior appears. Experimental data strongly support an interpretation of these properties based on the creation of oxygen vacancies in the SrTiO3 substrates during the growth of the LaAlO3 layer. When grown on SrTiO3 substrates at low P(O2), other oxides generate the same high mobility as LaAlO3 films. This opens interesting prospects for all-oxide electronics.

Co-Doped (La,Sr)TiO3−δ: A High Curie Temperature Diluted Magnetic System with Large Spin Polarization

We report on tunneling magnetoresistance (TMR) experiments that demonstrate the existence of a significant spin polarization in Co-doped (La, Sr)TiO(3-delta) (Co-LSTO), a ferromagnetic diluted magnetic oxide system (DMOS) with high Curie temperature. These TMR experiments have been performed on magnetic tunnel junctions associating Co-LSTO and Co electrodes. Extensive structural analysis of Co-LSTO combining high-resolution transmission electron microscopy and Auger electron spectroscopy excluded the presence of Co clusters in the Co-LSTO layer and thus, the measured ferromagnetism and high spin polarization are intrinsic properties of this DMOS. Our results argue for the DMOS approach with complex oxide materials in spintronics.

Full oxide heterostructure combining a high-TC diluted ferromagnet with a high-mobility conductor

We report on the growth of heterostructures composed of layers of the high-Curie temperature ferromagnet Co-doped (La, Sr)TiO_3 (Co-LSTO) with high-mobility SrTiO_3 (STO) substrates processed at low oxygen pressure. While perpendicular spin-dependent transport measurements in STO//Co-LSTO/LAO/Co tunnel junctions demonstrate the existence of a large spin polarization in Co-LSTO, planar magnetotransport experiments on STO//Co-LSTO samples evidence electronic mobilities as high as 10^-4 cm2/V s at T=10 K. At high enough applied fields and low enough temperatures (\mu H>=6 T, T<=4 K) Shubnikov-de Haas oscillations are also observed. We present an extensive analysis of these quantum oscillations and relate them with the electronic properties of STO, for which we find large scattering rates up to 10^(-11) s. Thus this work opens up the possibility to inject a spin-polarized current from a high-Curie temperature diluted oxide into an isostructural system with high mobility and a large spin diffusion length.

Controlling high-mobility conduction in SrTiO3 by oxide thin film deposition

SrTiO3 becomes a high-mobility metallic conductor when doped with oxygen vacancies at low concentrations (≥1016 cm−3). We show that the vacancy concentration in the SrTiO3 single crystal substrates could be controllably tuned by changing the thickness of oxide films (deposited by pulsed laser deposition at high temperature and low oxygen pressure). The obtained variation in the carrier density strongly influences the transport properties. The quantitative analysis of the experimental results leads toward new and accurate strategies for the design of multifunctional oxide heterostructures for electronics and spintronics.

Anisotropic charge dynamics in the quantum spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3

We have in detail characterized the anisotropic charge response of the dimer Mott insulator κ−(BEDT-TTF)2Cu2(CN)3 by dc conductivity, Hall effect,

Decoupled CuO 2 and RuO 2 layers in superconducting and magnetically ordered RuSr 2 GdCu 2 O 8

Comprehensive measurements of dc and ac susceptibility, dc resistance, magnetoresistance, Hall resistivity, and microwave absorption and dispersion in fields up to 8 T have been carried out on

Vacancy defect and carrier distributions in the high mobility electron gas formed at ion-irradiated SrTiO3 surfaces

{\mathrm{RuSr}}_{2}{\mathrm{GdCu}}_{2}{\mathrm{O}}_{8}

Enhanced superconductivity in Hf-base metallic glasses

with the aim to establish the properties of

Influence of doping on the Hall coefficient in Sr14− xCaxCu24O41

{\mathrm{RuO}}_{2}

Conduction anisotropy and hall effect in the organic conductor (TMTTF)2AsF6 : Evidence for luttinger liquid behavior and charge ordering

and