Effect of bombardment with different ions (H, He, Ar) on ordering transformation of Fe48Pt52 films

Fe48Pt52 thin films with a thickness of 50 nm were deposited at room temperature before undergoing glow-discharge-induced ion bombardment at 300 deg. C for 1 h. The energy of the incident ions was adjusted by applying a radio-frequency bias (Vb) from 200 to 600 V. H2, He, and Ar were used as the working gases. Significant ordering enhancement was only found in the H-ion bombarded films. The coercivity of such films is greatly increased from 0.5 kOe, for the sample without any bias, to around 8 kOe at Vb=200-600 V, which result is similar to that for a film annealed at 400 deg. C in a vacuum. This result suggests that H-ion bombardment has the effect of a 100 deg. C increase in annealing temperature. Microstructural studies reveal that the average grain size of the H-ion bombarded films is about 30 nm, which is much smaller than that of 400 deg. C-annealed films. The film thickness of He-ion bombarded samples decreases linearly as Vb increases because of the intensive sputtering effect. Under Ar-ion bombardment, most of the film is removed even at Vb=200 V