Magnetic Anisotropies and Magnetic Switching in Cobalt Films

The magneto-optical Kerr effect was used to investigate the role of the substrate and growth conditions in determining the magnetic switching behaviour of cobalt films in the thickness range 100-200 A supported by GaAs(001) and Si(111) substrates. The anisotropic magnetic hysteresis behaviour observed for Co/GaAs and Co/Si films is discussed in terms of coherent rotation of the magnetisation vector during magnetic switching. Equivalent films supported by glass substrates are found to be almost isotropic in-plane. The in-plane coercive and saturation fields are observed to lie in the range 20-80 Oe but perpendicular saturation fields of 25 and 19 kOe are found for the Co/Si and Co/GaAs systems, respectively, which substantially exceed the demagnetising field in each case. The measured perpendicular anisotropy fields differ strongly from the values for hcp and bcc Co and are attributed to the details of the interface and film structure. Strongly frequency dependent magnetic switching behaviour in these Co films is also reported.