Structural and transport properties of epitaxial Fe/ZnSe/FeCo magnetic tunnel junctions - art. no. 184422

The use of a semiconductor barrier in heteroepitaxy with ferromagnetic meta l electrodes describes a novel type of magnetic tunnel junctions. In this w ork, epitaxial Fe/ZnSe/FeCo magnetic tunnel junctions have been grown on Zn Se(001) buffered GaAs(001) substrates by molecular beam epitaxy. Alloying a small amount of Co with Fe in the base electrode provides a better seed ep ilayer for the growth of the ZnSe barrier compared to pure Fe as seen by tr ansmission electron microscopy. Detailed characterization of the FeCo surfa ce was performed by in situ scanning tunneling microscopy and revealed pyra mid-shaped defects of up to 60 Angstrom in height distributed on the FeCo s urface. Transport measurements on microfabricated tunnel junctions yielded up to 16% magnetoresistance at 10 K and the effect is attributed to spin po larized tunneling across the semiconductor barrier in the energy range of t he gap. The observed anomalous character of the magnetoresistance was attri buted to conduction through the pyramidal defects in the base FeCo layer.