High rotatable magnetic anisotropy in epitaxial L$1_0$CoPt(111) thin films

The evolution of the structural and magnetic properties in epitaxial film systems Co/Pt(111) of equiatomic composition during vacuum annealing has been presented. Annealing to the temperature of 400$^\circ$C does not lead to the variation of the structural and magnetic properties of the films, which indicates the absence of considerable mixing of the Co/Pt interface. With the increase in the annealing temperature from 400 to 750$^\circ$C, nanoclusters containing the main magnetically hard L$1_0$CoPt(111) phase epitaxially intergrown with the CoPt$_3$ phase are formed. High rotatable magnetic anisotropy has been found in the prepared films. In magnetic fields above the coercive force ($H>H_C=8$ kOe), the easy anisotropy axis with the angle of lag taken into account can be oriented in any spatial direction. Possible mechanisms of the formation of the rotatable magnetic anisotropy have been discussed. It has been assumed that the high rotatable magnetic anisotropy makes the main contribution to the magnetic perpendicular anisotropy in Co$_x$Pt$_{1-x}$ films.