Title :
Structural, electrical and magnetic properties of CoxC 1-x granular films
Author :
Weinforth, H. ; Somsen, Ch ; Rellinghaus, B. ; Carl, A. ; Wassermann, E.F. ; Weller, D.
Author_Institution :
Tieftemperaturphys., Duisburg Univ., Germany
fDate :
7/1/1998 12:00:00 AM
Abstract :
We report on the structural, electrical and magnetic properties of thin CoxC1-x granular films with metal volume fraction x=0.27 close to the percolation threshold xp≈0.3. The granular films are prepared by simultaneous UHV electron beam evaporation of high purity Co and C at room temperature. The structural properties are determined from transmission electron microscopy revealing small Co clusters with mean diameters of about 3 nm randomly dispersed in an electrically insulating C matrix. As-prepared films show insulating resistance behavior. Upon annealing to Ta=600°C in-situ measurements within the electron microscope show coalescence of the Co clusters forming continuous cluster-networks. Resistance versus temperature and magnetoresistance measurements on annealed films show a gradual change from insulating to metallic behavior. Room temperature measurements of the magnetic properties show the evolution of ferromagnetic behavior from superparamagnetic behavior upon annealing with a formation of an unusual perpendicular anisotropy
Keywords :
annealing; carbon; cobalt; composite materials; electrical resistivity; electron beam deposition; ferromagnetic materials; granular materials; insulating thin films; magnetic particles; magnetic thin films; magnetoresistance; metal clusters; metallic thin films; percolation; perpendicular magnetic anisotropy; superparamagnetism; transmission electron microscopy; vacuum deposited coatings; 600 degC; Co clusters; Co-C; CoxC1-x granular films; annealing; coalescence; continuous cluster-networks; electrical properties; electrically insulating C matrix; ferromagnetic behavior; insulating resistance behavior; magnetic properties; magnetoresistance; metal volume fraction; metallic behavior; percolation threshold; perpendicular anisotropy; room temperature; room temperature measurements; simultaneous UHV electron beam evaporation; small Co clusters; structural properties; superparamagnetic behavior; transmission electron microscopy; Annealing; Dielectrics and electrical insulation; Electric resistance; Electrical resistance measurement; Electron beams; Electron microscopy; Magnetic films; Magnetic properties; Temperature measurement; Transmission electron microscopy;
Journal_Title :
Magnetics, IEEE Transactions on
