Giant Magnetoresistance and Structure Of Phase-Segregated Epitaxial Metals*
- PDF / 1,275,238 Bytes
- 7 Pages / 420.48 x 639 pts Page_size
- 35 Downloads / 230 Views
GIANT MAGNETORESISTANCE AND STRUCTURE OF PHASE-SEGREGATED EPITAXIAL METALS* R.F. Marks, R.F.C. Farrow, G.R.Harp, S.S.P. Parkin, T.A. Rabedeau, M.F. Toney, A. Cebollada, IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, CA 95120-6099; N. Thangaraj, Kannan M. Krishnan, National Center for Electron Microscopy, Berkeley Laboratory, Cyclotron Road, Berkeley, CA 94720 "Lawrence This work was supported in part by ONR.
ABSTRACT Giant magnetoresistance, GMR, in thin metal films elicits attention due to its technological potential as well as its relevance to theory of exchange coupling. Epitaxial, phase-segregated ferromagnet/paramagnet mixtures have been grown by U HV evaporation. Such films show spontaneous formation of ferromagnetic clusters, leading to large values of GMR (40%/0 at room temperature) as grown. The growth of Co-Cu, Co-Ag, Fe-Ag and Permalloy-Ag films are described. Structural analysis by grazing-incidence small angle X-ray scattering (GISAXS) provides a measure of cluster size and characteristic spacing. Effects of growth temperature and subsequent annealing on GMR and film structure are described. Preliminary results of TEM examination of (001) Fe-Ag and Co-Ag granular films are presented for the first time. 1. INTRODUCTION Following active research in GMR of multilayer material systems, important GMR effects have been reported for phase-segregated films of Co-Cu [1,2] and Co-Ag [2] prepared by magnetron sputtering. Because of mutual immiscibility of components, Co-Cu, Co-Ag, Ni-Ag and Fe-Ag alloy films are presumed to contain small magnetic particles embedded in a nonmagnetic host matrix. To achieve a high magnetoresistance (MR) for sputtered alloy films, post-growth annealing was necessary to induce this phase segregation. In contrast, we report large values of magnetoresistance for as-deposited films of (111) and predominantly (001) oriented Co-Cu and Co-Ag grown at c-- 250 *C as well as for Fe-Ag, NiFe-Ag and NiFeCo-Ag. By selecting optimal growth temperature, epitaxial films with considerably larger GMR than that of comparable sputtered films can be realized, without additional annealing steps[3]. Both Co-Cu and Co-Ag are mutually insoluble (solubility
Data Loading...
