H. Vinzelberg | Searcharxiv

arXiv2010

Full spin switch effect for the superconducting current in a superconductor/ferromagnet thin film heterostructure

Superconductor/ferromagnet (S/F) proximity effect theory predicts that the superconducting critical temperature of the F1/F2/S or F1/S/F2 trilayers for the parallel orientation of the F1 and F2 magnetizations is smaller than for the antiparallel one. This suggests a possibility of a controlled switching between the superconducting and normal states in the S layer. Here, using the spin switch design F1/F2/S theoretically proposed by Oh et al. [Appl. Phys. Lett. 71, 2376 (1997)], that comprises a ferromagnetic bilayer separated by a non-magnetic metallic spacer layer as a ferromagnetic component, and an ordinary superconductor as the second interface component, we have successfully realized a full spin switch effect for the superconducting current.

cond-mat.supr-con↗

arXiv2001

The metal-insulator transition in amorphous Si_{1-x}Ni_x: Evidence for Mott's minimum metallic conductivity

We study the metal-insulator transition in two sets of amorphous Si_{1-x}Ni_x films. The sets were prepared by different, electron-beam-evaporation-based technologies: evaporation of the alloy, and gradient deposition from separate Ni and Si crucibles. The characterization included electron and scanning tunneling microscopy, glow discharge optical emission spectroscopy, and Rutherford back scattering. Investigating the logarithmic temperature derivative of the conductivity, w = d ln sigma / d ln T, we observe that, for insulating samples, w(T) shows a minimum increasing at both low and high T. Both the minimum value of w and the corresponding temperature seem to tend to zero as the transition is approached. The analysis of this feature of w(T,x) leads to the conclusion that the transition in Si_{1-x}Ni_x is very likely discontinuous at zero temperature in agreement with Mott's original views.

cond-mat.dis-nn↗