GIANT MAGNETORESISTANCE IN AS-GROWN EPITAXIAL-FILMS OF PHASE-SEPARATED CO-CU AND CO-AG

Giant magnetoresistance is reported in as-grown, epitaxial Co-Cu and Co-Ag alloy layers. The (111)- and (001)-oriented films were deposited onto (0001) sapphire and (001) rocksalt substrates, respectively, by co-evaporation in ultrahigh vacuum. Phase separation of the Co and Cu or Ag was obtained without any annealing after growth. The magnetoresistance at 4.2 K exceeded 50% and 70% in Co-Cu and Co-Ag films, respectively, and for films deposited at congruent-to 250-degrees-C a significant perpendicular magnetic anisotropy was observed in both magneto-resistance and magnetization studies. Grazing-incidence small-angle X-ray scattering indicates that the characteristic diameter and separation of Co clusters are approximately 25 angstrom and 76 angstrom, respectively, in (111) Co-Ag films grown at 250-degrees-C.