PURPOSE: To lower the magnetic permeability of a target and to improve the efficiency of using the target by forming the target material out of a Co-Cr-Ta alloy having a specific compsn. at the time of forming the thin film of a Co alloy by a magnetron sputtering method.

CONSTITUTION: The Co alloy consisting of 5 to 20 atomic % Cr, 1 to 10 atomic % Ta and the balance Co and having ≥30 Rockwell hardness is used as the material of the target 2 having a magnet 3 on the rear surface at the time of forming the thin film of the Co alloy by the magnetron sputtering method on a substrate 1. This target 2 has the high magnetic anisotropy of crystals and the small magnetic permeability as the target is magnetically hardened and, therefore, the rate at which the magnetic lines of force by the magnet 3 passes the inside of the target 2 is small and a powerful magnetic field is formed above the target 2 to increase the ionization efficiency during glow discharge. Since the plasma density is increased, the sputtering efficiency of the target alloy 2 is improved.