Magnetic and microstructure properties of Ag/Co /Ag granular film

摘要

Ag/Co/Ag nanogranular films were prepared by DC magnetron sputting onto glass substrates at room temperature .Then one series of films are as-deposited and the other series of films are annealed at 400℃for 30 min . In this paper both the in plane and the perpendicular magnetic properties of the films are investigated by vibrating sample magnetometer (VSM) methods. The magnetic hysteresis loop, the isothermal remanence (IRM), and the DC demagnetization (DCD) remmanence and the moment decay with the time (M-t plot) can be measured by VSM. The perpendicular coercivity of the film annealed at 30min is up to 1105Oe. However maximum coercivity is only 535 Oe in as-deposition film. X-ray diffraction profiles show Co nanograins are formed as the hexagonal-close-packed (hcp) and the peak of the annealed films is more height than the as-position films .The thickness of Ag layer and annealing intensively affect the structure and magnetic properties of the films. The Scanning probe microscope (SPM) was used to get the surface morphology (AFM images) and magnetic domain structures (MFM images). The results of the δM plots and the dM dH Curve indicate that the intergranular interaction in the as-deposition film seem to be of exchange coupling, while those in annealed films the exchange coupling reduces and the magneto static interactions take plays. From the time dependence of the magnetization （M-t）and DCD experiments, the magnetic activate volume (Va) can be obtained, which determines the thermal stability of magnetic recording media.