Shunichi Yamanaka

Preparation of High-Coercivity Co–Pt Alloy Films by Target-Facing Type of High-Rate Sputtering

Co1-xPtx (0x0.2) thin films were prepared by using a Target-Facing type of high-rate sputtering (TFTS). The films deposited at lower argon gas pressure PAr(5 mTorr) have only a low coercive force Hc ( 1 kOe) can be obtained at a Pt content of above 11 at%. These films, whose crystallites are oriented randomly, also have a large inplane uniaxial magnetic anistropy constant K1 (\cong2.5×106 erg/cc) and excellent hysteresis loop squareness (S\cong0.87, S*\cong0.98).

Nickel Ferrite Thick Films Deposited by Vacuum-Arc Discharge

Stoichiometric nickel ferrite films 10~100 µ thick have been prepared by an arc evaporation in a vacuum of 10-4 torr of the material sintered with the starting mixture (Ni0)0.62(Fe2O3)0.38, and subsequent heat treatment in air at 1250~1350°C. They have a saturation magnetization value σs of 51 gausscm3/g agreed with the value for the bulk nickel ferrite. Their X-ray diffraction patterns and Mossbauer absorption spectra indicate that they may be composed of the polycrystalline particles with a homogeneous ion distribution and an inversed spinel structure. However, the as-deposited film is composed of the spinel, rock-salt and nickel types of small crystalline particles and the fine amorphous particles, and has σs of 17 gausscm3/g. Since each component ion is distributed inhomogeneously in the particles, the heat treatment below 1200°C oxidizes them in different ways. Consequently, the structure and σs of the film has a complex dependence on the heating temperature.

Vacuum-Arc Evaporations of Ferrites and Compositions of Their Deposits

The evaporation in a vacuum of the order of 10-4 torr with a current of 14 A is investigated by electron-microscopic observation of the surface of the ferrite source, spectroscopic analysis of the vapour emission and composition analysis of the discharge atmosphere. Ferrite is thermally decomposed to release oxygen gas in the region of cathode spots. Most of the constituent metals are evaporated in the state of atom. The difference in cation ratio Me/Fe between the source and its deposit is rather small, where Me is one of Mg, Mn, Co, Ni, Cu and Zn. The evaporation rate of each metal depends on the temperature at which its vapour pressure is 10-2 torr. If the source composition is carefully controlled, it is possible to make the cation ratio of its deposit adequate for typical simple ferrites, and even mixed ferrites, such as Ni0.3Zn0.7Fe2O4 and (N0.85Cu0.15)0.94Fe2.06O4.

High rate deposition of magnetic films by sputtering from two facing targets

Abstract A new type of cathode sputtering apparatus with two facing targets was developed to prepare magnetic films at a high deposition rate without the extreme rise of the substrate temperature. When two disks of iron, nickel and ferrite were used as targets, the maximum deposition rates obtained were approximately 4000, 5000 and 1000 A/min, respectively. The substrate temperature was not elevated above 200°C during sputtering.

Deposition of Silicon Nitride Films by High Rate Reactive Sputtering

Amorphous silicon nitride fims have been deposited at a high rate on the substrate without extreme rise of temperature by dc reactive sputtering in the atmosphere of a mixed gas of argon and nitrogen using a planar magnetron type of sputtering apparatus. The composition and deposition rate of the films were strongly depended on the partial pressure of nitrogen PN2. Deposition rate and the content of silicon in the films decreased with increasing PN2 especially in the range of PN2=3~5 m Torr and became nearly constant in the range of PN2>5 m Torr. The refractive index, etch rate, resistivity, infrared absorption, transmittance and latent stress of obtained films were determined. The films deposited in the atmosphere of PN2>5 m Torr exhibited excellent properties even if they were deposited at very high deposition rate above 1000A/min.

Variable Surface Acoustic Wave Delay Line Consisting of a Magnetic Thin Film on a LiNbO3 Substrate

The variable surface acoustic wave (SAW) delay line was constructed in such a way that the amorphous TbFe2 film was deposited by co-sputtering on the wave- propagating surface of the LiNbO3 substrate. When the thickness of the magnetic film was about 2.5 µm, the SAW velocity in the range of frequency of 42 MHz could be continuously varied up to 0.27% by applying the magnetic field of a few kilo-oersted. The result of the calculation based upon a simple model suggested that the variation in the SAW velocity was mainly attributed to the electromechanical coupling factor k15 which dominated the interaction between magnetic moments and SAWs in the magnetic material.