Magnetization process of high anisotropy CoPt nanosized dots

Dot arrays with diameter ranging from 80 to 245 nm are made of Co₈₀Pt₂₀ films with large perpendicular anisotropy. Magnetic properties are investigated by detecting the anomalous Hall effect. The all arrays show angular dependence of remanent coercivity similar to coherent rotation. The result shows that reversal process is independent of dot diameter. The energy barrier height of magnetization reversal is estimated as 1.0×10^-10 erg for the array consists of 140-nm-diameter dots. From the energy value, the switching volume is estimated as equivalent to the volume of a physical grain in the film. The results indicate that the reversal process starts from a nucleation of a "reversed grain" followed by propagation process.