Preparation and Gas Addition of Soft Magnetic Pure Iron Thin Film by Dual Ion Beam Sputtering

Pure iron thin films with soft magnetic properties and good chemical stabilities have been prepared by Dual Ion Beam Sputtering (DIBS). Four kinds of gas, that is, hydrogen, helium, nitrogen and argon were introduced respectively to the auxiliary ion source as the additional element in the film and also for the purpose of bombardment during deposition. The dependence of crystal structure and magnetic properties of the films on the preparation condition, especially, on the effect of various gases added in the films by ion bombardment onto the depositing film surface, has been investigated.Saturation magnetization 4πMs of iron film including gas atoms is usually smaller than that of bulk iron which has 4πMs of 21.5kG. For example, 4πMs of the film prepared by conventional planer magnetron sputtering remains about 15kG. Such a remarkable difference in 4πMs may be primarily attributed to the considerable amount of argon atoms included in the film due to argon pressure as high as 10mTorr. It may be also caused by high energy particles bombarding onto the iron film surface during deposition. On the other hand, pure iron thin films prepared by Dual Ion Beam Sputtering can have 47Ms as high as 21.5kG, and coercive force Hc as low as about 4 Oe by controlling the ratio of sputtering iron atoms to argon gas atoms, impinging onto the substrate, and the arrival energies both of them. Magnetic properties and crystal structures of the iron thin films depend significantly on the kind of added gas. In this study, it has been found that bombardment and addition of adequate gas atoms with proper energy results in an improvement of atomic ordering and microscopic uniformity in the films.