Conductance anisotropy and linear magnetoresistance in La(2 - x)Sr(x)CuO4 thin films.

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La(2 - x)Sr(x)CuO(4) (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance R(xy) in zero magnetic field. It is demonstrated that the sign of R(xy) depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of R(xy) is sensitive enough to detect the cubic-tetragonal phase transition of the SrTiO(3)(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the Hall resistivity as [Formula: see text], with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper.

Magnetic effects at the interface between non-magnetic oxides.

The electronic reconstruction at the interface between two insulating oxides can give rise to a highly conductive interface. Here we show how, in analogy to this remarkable interface-induced conductivity, magnetism can be induced at the interface between the otherwise non-magnetic insulating perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the interface is found, together with a logarithmic temperature dependence of the sheet resistance. At low temperatures, the sheet resistance reveals magnetic hysteresis. Magnetic ordering is a key issue in solid-state science and its underlying mechanisms are still the subject of intense research. In particular, the interplay between localized magnetic moments and the spin of itinerant conduction electrons in a solid gives rise to intriguing many-body effects such as Ruderman-Kittel-Kasuya-Yosida interactions, the Kondo effect and carrier-induced ferromagnetism in diluted magnetic semiconductors. The conducting oxide interface now provides a versatile system to induce and manipulate magnetic moments in otherwise non-magnetic materials.