M. Nagakubo

Effects of hydrogen and nitrogen ion bombardments on soft magnetism of iron films during double‐ion‐beam sputtering

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.

Effects of annealing and periodic ion bombardment on the soft magnetism of FexN films by a double ion beam sputtering system

Fe films with low nitrogen content have been prepared by using a dual ion beam sputtering apparatus. The effects of annealing at 300 °C for after‐treatment of as‐deposited films and the effects of periodic nitrogen ion bombardment onto growing Fe layers for growth process on their structure and magnetic properties have been investigated. The Hc of Fex N single layer films with nitrogen content of 2–3 at. % bombarded continuously by a mixture of argon and nitrogen ions decreased noticeably after annealing at 300 °C without significant decrease of saturation magnetization 4πMs. On the other hand , the Hc of the Fe/Fex N multilayered films bombarded periodically by the nitrogen ions at an accelerating voltage of 150 V decreased drastically, and took a minimum Hc of 1.5 Oe at proper cycle time tp. These results may be attributed to the relaxation of internal stress in films by annealing and the modification of microscopic morphology by ion bombarding, respectively.

Semi-hard magnetism of iron nitride films prepared by double ion beam sputtering

The semihard magnetic properties and crystal structure of iron nitride films prepared by double ion beam sputtering have been investigated. The films consisted of Fe layers and Fe/sub x/N layers bombarded by nitrogen ions during deposition. The films were annealed at 300 degrees C for 3 h after deposition. When the thickness ratio of Fe layers to Fe/sub x/N was adjusted to a value below 10 for films with the appropriate number of pairs of layers, the as-deposited films had coercivity, H/sub c/ of about 100 Oe and saturation magnetization, 4 pi M/sub s/, of about 18 kG. Annealing of films composed of 19 pairs of Fe and Fe/sub x/N layers with a relative thickness ratio of 5 resulted in a large increase in film coercivity from less than 100 Oe before anneal to 500 Oe postanneal. A moderate decrease in film 4 pi M/sub s/ was also seen after the annealing process. X-ray diffractometry showed the presence of zeta -Fe/sub 2/N phase in these films. A moderate decrease of 4 pi M/sub s/ and a marked increase of H/sub c/ may be caused by suppressing the growth of zeta -Fe/sub 2/N crystallites and the short-range irregularity at interfaces between Fe and Fe/sub x/N layers. >

Magnetism and crystal structure of Fe/Si multi-layered films prepared by ion beam sputtering

Fe/Si multilayered films have been prepared by ion-beam sputtering. The dependence of their crystal structure and magnetic properties on the individual layer thicknesses has been investigated. The annealing effects for those films have also been examined. The films with Fe and Si layer thickness of more than 85 AA clearly exhibited multilayered microstructure. H/sub c/ of the films with delta /sub Fe/ of 10 AA had a minimum value of 1.5 Oe at delta /sub Si/ of about 4 AA. For the films with delta /sub Si/ of 20 AA, H/sub c/ had a relatively high value of about 50 Oe; it reached its minimum value of about 2 Oe at delta /sub Si/ of about 40 AA after annealing at 300 degrees C for 1 h. >

Magnetic and structural characteristics of Fe/Si multilayered films bombarded by Ar ions

Fe/Si multilayered films were deposited by using a dual ion-beam sputtering apparatus, and the effect of Ar ion bombardment during deposition on the structure, internal stress, and magnetic properties was investigated. For the films without ion bombardment, tensile stress was induced in the Fe layers. On the other hand, for those with ion bombardment, compressive stress was induced in the Fe layers, and coercivity became as low as about 6 Oe. Consequently, Ar ion bombardment is effective to get soft magnetism for the multilayered films because of changing the structure and internal stress.

Preparation of aluminum thin films by the facing targets sputtering system

Abstract The facing targets sputtering (FTS) system, typical of plasma-free sputtering systems, was used to deposit aluminum thin films composed of very fine grains with a smooth surface, large hardness and low resistivity. When the argon gas pressure P Ar was also low as 10 −1 Pa, the aluminum films deposited at a bias voltage to substrate V b of −40 V became smoother, more reflective and harder. The films deposited at a V b of −100 ∼−160 V revealed a definite (111) orientation of the aluminum crystallites parallel to the film plane. The resistivity ϱ of the films deposited at a P Ar below 10− Pa was almost equal to that of bulk aluminum.

Magnetism and crystal structure of Fe/Al/Si films prepared by dual-ion-beam sputtering

Fe/Al/Si multilayered films have been deposited using an ion‐beam sputtering apparatus. The effects of ion bombardment onto growing film surfaces and the effects of annealing after deposition on their crystal structure and magnetic properties have been investigated. The thicknesses of Fe, Al, and Si layers were adjusted at the value corresponding to the Sendust composition. Then the Fe layer thickness was set at 10 A. Sharp peaks in small‐angle x‐ray diffraction diagrams of the as‐deposited films clearly revealed the multilayered structure. Such peaks for films bombarded by argon ions at the acceleration voltage (Vb) of above 100 V during deposition were not observed. In addition, the films annealed at the temperature above 300 °C for 3 h showed the DO3 and/or B2 type of crystal structure and exhibited coercivity (Hc) below 3 Oe. It has been found that the Fe/Al/Si multilayered films can be alloyed at relatively low substrate temperature by the aid of ion bombardment during deposition. Annealing after dep...