Structure and magnetoresistance effect in granular Ag-Ni alloys prepared by gas flow condensation technique

Giant magnetoresistance (GMR) effect in heterogeneous granular Ag-Ni alloys, prepared by utilizing coevaporation of the metals in continuous He flow, is reported. The average grain size, determined from x-ray diffraction (XRD) data, increases from 11 to 28 nm with increasing He pressure. The transmission electron microscope analysis revealed the presence of Ag and Ni isolated grains which give rise to coalescence. The nitrogen adsorption measurements show a decrease of the surface area with increasing pressure confirming the XRD data. Electrical measurements revealed a GMR effect as large as 7%, at room temperature and a magnetic field H = 1 T, on the specimen prepared with a final pressure of 800 Pa. (C) 1998 American Institute of Physics. [S0021-8979(98)09613-3].