Showing papers by "Barry L. Zink published in 1998"

Tunneling And IR Spectroscopy On Giant Magnetoresistive Amorphous Rare Earth-silicon Alloys

Abstract: Spin-tunneling and tunnel magnetoresistance (TMR) attract much attention at the moment because of their promise for magnetic sensors and memory devices. The TMR is analyzed for ferromagnet-insulatorferromagnet junctions, including half-metallic systems. Direct tunneling is shown to be mainly responsible for the observed behavior of conventional junctions, and it is compared with impurity-assisted and resonant spin tunneling. Impurity-assisted tunneling decreases the TMR down to a few percent with conventional electrodes, and spin-flip scattering from defect states will further reduce this value. The same is generally true of a resonant diode type of structure. The model applies to half-metallic systems with 100% spin polarization, where the change of resistance in the absence of spin-flips may be arbitrarily large. Even in the case of imperfect magnetic configurations the resistance change can be a few lo00 percent, as illustrated by CQ-based systems with matching oxides.' Relevance of these results for magnetic oxides with colossal MR will be discussed.