Tunable conductance of magnetic nanowires with structured domain walls

We show that in a magnetic nanowire with double magnetic domain walls, quantum interference results in spin-split quasistationary states localized mainly between the domain walls. Spin-flip-assisted transmission through the domain structure increases strongly when these size-quantized states are tuned on resonance with the Fermi energy, e.g. upon varying the distance between the domain walls which results in resonance-type peaks of the wire conductance. This novel phenomena is shown to be utilizable to manipulate the spin density in the domain vicinity. The domain walls parameters are readily controllable and the predicted effect is hence exploitable in spintronic devices.Comment: 4 pages with 4 figure

Low Voltage I-V Characteristics in Magnetic Tunnel Junctions

We show that elastic currents that take into account variations of the tunnel transmitivity with voltage and a large ratio of majority to minority spin densities of states of the $s$ band, can account for the low voltage current anomalies observed in magnet-oxide-magnet junctions. The anomalies can be positive, negative or have a mixed form, depending of the position of the Fermi level in the $s$ band, in agreement with observations. Magnon contribution is negligible small to account for the sharp drop of the magnetoresistance with the voltage bias.Comment: 8 pages, 3 postscript figure

A two band model for Superconductivity: Probing interband pair formation

We propose a two band model for superconductivity. It turns out that the simplest nontrivial case considers solely interband scattering, and both bands can be modeled as symmetric (around the Fermi level) and flat, thus each band is completely characterized by its half-band width $W_{n}$ (n=1,2). A useful dimensionless parameter is $\delta$, proportional to $W_{2}-W_{1}$. The case $\delta =0$ retrieves the conventional BCS model. We probe the specific heat, the ratio gap over critical temperature, the thermodynamic critical field and tunneling conductance as functions of $\delta$ and temperature (from zero to $T_{c}$). We compare our results with experimental results for $MgB_{2}$ and good quantitative agreement is obtained, indicating the relevance of interband coupling. Work in progress also considers the inclusion of band hybridization and general interband as well as intra-band scattering mechanisms.Comment: 7 pages, 5 figures (in postscript format). PACS numbers: 74.20.-z, 74.20.Fg, 74.70.A