The effect of the Ar ion milling process on tunnel magneto-resistance was investigated by using Ar ion milling to make a small hole at the center of the active area of a junction prepared by means of metal masks. Metallic short-circuiting through the material redeposited during Ar ion milling was evaluated by comparing the tunnel resistance before and after the process. The amount of redeposited material was small in the samples produced by the milling process with a higher incident angle of Ar ions. Small Ni-Fe/Co/Al-O/Co junctions with various active area ranged from 9 to 104 μm2 were also fabricated. The tunnel resistance increased in inverse proportion to the active area. Many junctions showed a TMR ratio of 9%-13%, which was as large as the value for junctions prepared by means of metal masks.
