Fe/Al multilayered films with the thicknesses of the Fe and Al layers (δFe and δAl) below 300 Å have been prepared by means of an ion-beam sputtering method, and the dependence of their crystal structure and magnetic properties on δFe and δAl has been investigated. The saturation magnetization 4πMs and the coercivity Hc of the multilayered films decreased monotonically and the d(110) spacing of α-Fe crystallites in the Fe layers increased as δFe decreased in the range below 100 Å for δAl of 20 Å. Such an increase in d spacing was removed substantially by annealing at 300 °C in vacuum. The x-ray diffractometry of the multilayered films with δFe of 100 Å and δAl below 15 Å indicated only the (200) orientation of α-Fe crystallites. In the range of δAl from 20 to 15 Å the preferentially oriented plane of Fe crystallites changed from (110) to (200) and Hc took a minimum value lower than 4 Oe. These results might be attributed to the alternate epitaxial growth at the interfaces between the Fe and Al layers.
The dependence of the crystal structure and magnetic properties of iron films on preparation conditions has been investigated in detail by using a double-ion-beam sputtering system. During sputtering of an iron target by argon ions, the growing surfaces of iron films were bombarded by nitrogen or hydrogen ions with different kinetic energies below 500 eV. It has been found that these ions changed significantly the film structure and magnetic properties through the process of collision and reaction with iron atoms at the surface layer of growing film. As a result, the small amount of hydrogen or nitrogen added into iron films by ion bombardment improved effectively the soft magnetic properties of iron films. The iron films with saturation magnetization 4πMs as large as 22 kG and coercive force Hc as low as about 5 Oe were prepared by adjusting the accelerating voltage in the range of 100–300 V and the partial pressure of hydrogen or nitrogen in the range of 10−4 –10−5 Torr.
Fe films have been deposited by using dual ion beam sputtering apparatus under various conditions, and the dependence of their magnetic properties and morphology on preparation parameters such as film thickness, δt, and argon gas pressure, PAr, have been investigated in detail.
The saturation magnetiza ion 4πMs of the specimen films did not change remarkably with 6t in the range of 50 ∼1000nm. However, with decrease of 6t below 50 nm, 4πMs decreased to less than 20 kG and coercivity Hc increased to more than 16 Oe. As PAr increased from 0.5 to 1.6 mTorr without ion bombardment, 4πMs decreased to less than 20 kG and Hc increased to about 20 Oe. The SEM micrographs of these films deposited at higher PAr showed the columnar structure. On the other hand, the films deposited at Yower PAr and ones bombarded by argon ions with proper kinetic energy during deposition did not present any texture and exhibited better soft magnetism. Such a morphology may be attributed to the difference in arrival energy of sputtered Fe particles to film surface and related closely to soft magnetism. It has been found that the dual ion beam sputtering method can control 4πMs and Hc with changing PAr and so prepare Fe films with superior soft magnetism by adjusting the kinetic energy of bombarding argon ions at lower PAr.
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