Reactively sputtered MgAl2O4 barrier layers for Heusler tunnel junctions

Epitaxial MgAl2O4 thin films were deposited on a lattice-matched Heusler alloy, Fe2CrSi, by reactive magnetron sputtering of an MgAl2 target in an Ar+O-2 atmosphere. Epitaxial Fe2CrSi/MgAl2O4 junctions were obtained by inserting an ultrathin MgAl2 interlayer, which worked as a protective layer for oxidization at the surface of the Fe2CrSi. The growth of MgAl2O4 was found to be very sensitive to the MgAl2 thickness and the oxygen partial pressure during the deposition of MgAl2O4. Both epitaxial growth and characteristics of the efficient tunneling barrier were obtained in an Fe2CrSi/MgAl2O4 (3 nm)/CoFe tunneling device for MgAl2O4 thin films grown by reactive sputtering. The present epitaxial MgAl2O4 barrier deposited by reactive sputtering is expected to realize high performance spintronic devices.