Abstract
Three kinds of Fe films, without Ar bombardment [BNON], with Ar bombardment after deposition [BAFT], and with Ar bombardment during deposition [BDUR], were prepared by dual ion-beam sputtering. The relationship between the morphology and the magnetic characteristics of the Fe films was investigated as a function of the film thickness tF in the wide range between 0.5 and 600 nm. The sputtering voltage and current were fixed at 1200 V and 50 mA, respectively. The Ar bombardments for BAFT and BDUR were carried out at an ion acceleration voltage of 200 V. The features of the film growth were very different according to the type of bombardment. The BNON films changed from an island structure to a layer structure at tF between 8.0 and 16 nm. The BAFT and BDUR films were revealed smoother surfaces than BNON and echibited a layer structure at tF above 1.0 nm. However, the saturation magnetization 4πMS of BDUR abruptly decreased at tF below 8.0 nm, since the Ar bombardment knocked Fe atoms into the surface region of the glass substrate during the initial growth stage. On the other hand, 4πMS of BNON and BAFT took an almost constant value of 21.5 kG with a fluctuation of about 5%. The coercivity Hc of BAFT had lowest value all the films at tF below 4.0 nm. These results indicate that Ar bombardment after deposition is useful for preparing ultrathin Fe films with excellent soft magnetic properties.
