Tunneling I-V Characteristics for a Superconductor-Insulator-Half metal Junction

Half-metals are compounds with a 100% spin polarization in one direction: they are metallic for one spin direction but insulators, or semiconductors, for the other direction. From the viewpoint of the density of states (DOS) it is finite at the Fermi level for one spin direction and negligible small for the other. In this work the current vs. voltage characteristics I-V, for a Superconductor- Insulator-Half metal have been calculated with a simple and straightforward procedure which essentially involves a product of the corresponding DOS for the electrodes of the junction. Nb, a BCS superconductor, and CrO₂, a well-known half-metal, have been considered as electrodes which are separated by a perfect insulator to form the SC-I-HM tunnel junction. Our results show that the I-V characteristics for a SC-I-HM junction are useful for obtaining the majority spin part of the DOS and the gap for the minority spin part or as an experimental confirmation of theoretical calculation of DOS for a half-metal; furthermore, such junctions may be used as a spin valve for certain polarization voltages or as a component of a more sophisticated spintronic device. (paper)