Structural and magnetic properties of Co65C35 nanocomposite films preparedby pulsed filtered vacuum arc deposition

In this paper, the Co65C35 nanocomposite film was prepared by pulsed filter ed vacuum are deposition. Subsequent thermal annealing was performed in a v acuum furnace (similar to 8 X 10(-4) Pa) at various temperatures. The films were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and magnetic force microscopy (MFM). The magneti c properties were measured by a SQUID magnetometer. The as-deposited film w as found to be amorphous and soft ferromagnets. No obvious magnetic domain structures can be observed in the MFM image, indicating the low anisotropy in the amorphous film. After annealing at a temperature between about 300 d egreesC and 350 degreesC, the as-deposited amorphous films went through a m eta-stable stage at which a cobalt carbide phase and hexagonal close-packed (hcp) crystalline cobalt co-existed. Upon increasing of annealing temperat ure to 400 degreesC, the carbide phase decomposed into hcp crystalline coba lt nanograins and graphite-like carbon. Clear MFM images with obvious long- range magnetic structures can be obtained in the annealed films. The streng thened MFM images contrast implied the enhanced magneto-crystalline anisotr opy owing to the nanocrystallization of Co grains within the films. The mag netic hardening was demonstrated by the round-shaped magnetic hysteresis lo ops. (C) 2001 Elsevier Science B.V. All rights reserved.