Annealing effects on magnetic properties of CoCr sputtered films were investigated. The anneal in air near 400°C causes the considerable increase of the saturation magnetization M
s, the perpendicular coercivity H
c(

) and the perpendicular anisotropy K
u. These increments were interpreted by the formation of antiferromagnetic Cr
2O
3surrounding column boundaries, which was supported by the depth profiles of AES and the spectrum of ESCA. Furthermore, the variations in magnetic properties are fairly suppressed by coating the film surface with a SiO
2or AlN layer.