The influence of rare earth (RE) constituents on the magnetic and optical properties of RE-FeCo thin films

The polar Kerr effect and perpendicular anisotropy of various rare-earth (RE)-FeCo films were measured and were found to have different dependencies upon the RE composition of the films. The polar Kerr effect was found to be largest for those films where Gd dominated the RE composition. Also, the polar Kerr effect was seen to decrease monotonically as increasingly heavy RE elements from Gd to Er dominated the RE composition. The other RE elements in this range are Tb, Dy, and Ho. In contrast, the perpendicular anisotropy of the same films was seen to be largest when Tb dominated the RE composition. The perpendicular anisotropy decreased rapidly when Gd was substituted for Tb and decreased gradually when increasingly heavy RE elements were substituted for Tb. It is also shown that the dependence of the Curie temperature upon RE composition for these RE-FeCo films correlates strongly with the dependence of the Curie temperature upon composition for pure RE alloys over a similar range of elements