Y. Hoshi

Facing targets type of sputtering method for deposition of magnetic metal films at low temperature and high rate

A new type of cathode sputtering apparatus with two targets facing each other has been developed to prepare magnetic films at a high deposition rate without the extreme rise of the substrate temperature. When two disks of iron and nickel were used as targets, the maximum deposition rates obtained were approximately 4000 and 5000 A/min, respectively. The substrate temperature was not elevated above 200°C during sputtering. The high rate deposition of Mo permalloy films also was attempted by co-sputtering of two facing targets composed of disks of iron and nickel and chips of molybdenum. The Vickers hardness of the obtained Mo permalloy films was about 900 and the typical values of permeability at 1 MHz magnetic field and coercive force at dc magnetic field of them were about 2500 and 0.16 Oe, respectively.

Ba–ferrite thin‐film disk for perpendicular magnetic recording

The authors have prepared Ba–ferrite film disks and evaluated their magnetic read/write characteristics. The c‐axis‐oriented Ba–ferrite thin films were formed epitaxially on c‐axis‐oriented ZnO films by means of a targets‐facing‐type sputtering system. The direction of easy magnetization in the film with perpendicular crystalline anisotropy is almost perpendicular to the film plane. Thus, the perpendicular remanence is more than 60 times as large as the in‐plane one. The simple Ba–ferrite films, however, have a coercive force, Hc⊥ above 2 kOe which is too large to write on by means of a conventional head. The substitution of In3+ in the Ba–ferrite films makes the Hc⊥ values decrease to about 1 kOe without increasing the critical temperature, Tcritical, of c‐axis orientation. The read/write characteristics of the films were measured with a MnZn–ferrite ring head. The reproduced signal exhibits clear dipulsive waveforms as the dipulse ratio exceeds 0.7. Furthermore, the overwrite ratio decreases below −28 d...

Formation of Ba-ferrite films with perpendicular magnetization by targets-facing type of sputtering

Ba-ferrite films have been prepared by means of Targets-Facing type of sputtering method which is very useful to prepare magnetic films at high rate without any bombardment of high energy particles such as γ-electrons and negative ions emitted from the targets and is favorable to obtain stoichiometric films of good quality. C-axis orientation of the films depends strongly on substrate temperature and crystal structure of substrate. C-axis well oriented BaM films are deposited on amorphous materials such as a-SiO 2 . The deposited films of 3000 A in thickness have ΔΘ 50 less than 1 degree, magnetic anisotropy constant of 3.2\times10^{6} erg/cc, saturation magnetization of 380 emu/cc and coercive force of 1.3 kOe. These films reveal much better c-axis orientation and surface smoothness than the films deposited by DC diode type of sputtering method and have almost the same composition as that of the targets.

Preparation of barium ferrite films with perpendicular magnetic anisotropy by DC sputtering

Barium ferrite thin films with perpendicular magnetic anisotropy have been prepared by DC diode sputtering. When a sintered target with appropriate composition was used, c-axis oriented Ba ferrite film was obtained whose easy direction of magnetization was normal to the film plane. Its saturation magnetization Ms, coercive force Hc\perp and magnetic anisotropy constant Ku were 400 emu/cc, 680 Oe and 1.67 × 106erg/cc, respectively. Ba ferrite films may be usable as are Co-Cr films as a perpendicular magnetic recording medium.

Preparation of Ba-ferrite films for perpendicular magnetic recording by RF targets facing type of sputtering

A rf Targets Facing Type of Sputtering(rf-TFTS) apparatus was used to deposit hexagonal magnetoplumbite type of Ba ferrite (BaO.6Fe 2 O 3 : BaM) films with c-axis orientation at high rate. Although high rate sputtering of BaM was possible under stable conditions in rf-TFTS, the film composition changed drastically with total gas pressure P total and input power P av during sputtering. These changes in film composition corresponded well to the change in the potential difference Vd between plasma and wall, that is, the deficiency in Ba content in the films increased as V d increased. These results indicate that the change in composition is caused by ion bombardment of the substrate during sputtering (i.e., Ba atom is resputtered preferencially), since the ions in plasma can bombard the substrate with energy about e.V d . The value of V d decreases as P total or P av increases and the BaM films with stoichiometric composition were obtained at high P total or at high P av . Therefore, sputtering must be performed under the condition of high sputtering power or of high sputtering gas pressure, where V d becomes small, to deposit stoichiometric BaM films.

Effect of additional element (Fe, Zr, Ta) for Co‐Cr films deposited by targets facing type of sputtering

In order to improve both magnetic properties and wear resistance of Co‐Cr films for perpendicular magnetic recording media, the effect of the addition of a small amount of Fe, Zr, and Ta to the Co‐Cr binary alloy films has been investigated. They were deposited with a targets facing type sputtering (TFTS) apparatus. (i) The addition of a small amount of Fe (<5 at. %) causes a significant decrease of the effective perpendicular magnetic anisotropy K⊥ (K⊥=Ku−2πM2s). The K⊥ has a negative value at Fe content above 1 at. %. Consequently, the recording characteristics become worse as Fe content increases. (ii) The addition of Zr leads to a remarkable decrease of grain size and improvement of surface smoothness along with an increase of wear resistance. It also causes evident decrease in Ku and saturation magnetization Ms. However, both K⊥ and remanence ratio Mr⊥/Mr∥ are increased by the addition of a small amount of Zr up to 0.5 at. %, though they decrease steeply with further increase of Zr content above 1 at...

Sputter deposition and read/Write characteristics of Ba-ferrite thin film disk

The nucleation mechanisms and the composition change in Ba ferrite films deposition by means of the Targets Facing Type of Sputtering system have been discussed in detail. In addition, an attempt to control their magnetic properties has been made and read/write characteristics of the films prepared on the disk substrates have been evaluated. The single phase Ba ferrite films composed of fine graines are deposited epitaxially on the c-axis well oriented ZnO layer even in the nucleation stage under a wide range of preparation conditions. Moreover, the film composition, the crystal structure and the magnetic properties depend strongly on oxygen partial pressure. The films sputtered from the targets of n=5 and 6 in the BaO.nFe203 system exhibit good crystallographic and magnetic properties under the wider range of sputtering conditions. The coercive force Hc can be decreased without increasing the critical temperature of c-axis orientation by substitution of In3+for Fe3+. Furthermore, the D50 increases and overwrite decreases with increase of In3+content. Consequently, high density perpendicular recording with D 50 of 88 kFRPI has been achieved by using a narrow gap (0.4 μm) ring head.

Properties of amorphous Co–Ta and Co–W films deposited by rf sputtering

Magnetic and thermal properties of Co100−xTax(11≤x≤25) and Co100−xWx(13≤x≤25) amorphous films deposited by rf diode sputtering have been investigated. In both systems, structural changes of these films from crystalline to amorphous lead to a drastic decrease of their coercive force Hc and the absolute value of saturation magnetostriction λs, where λs is negative. Since magnetic properties and structure of the amorphous Co–Ta and Co–W films depend significantly on the argon gas pressure PAr, the PAr must be adjusted to the proper value during sputtering to obtain films with soft magnetic properties. Typical magnetic properties of Co–Ta and Co–W amorphous films are as follows: (i) Co–Ta: 4πMs≤11 kG, −λs≤2×10−6, Hc≤0.4 Oe. (ii) Co–W: 4πMs≤11 kG, −λs≤8×10−6, Hc≤4.0 Oe. The crystallization temperature Tx of the amorphous Co–Ta films is above 700 K and Tx increases with the increase of Ta content in the films. Tx of amorphous Co–W films is above 940 K. In this alloy system, however, structure relaxation occurs ...

Influence of O2 and N2 addition on the perpendicular magnetic anisotropy of Gd‐Co amorphous films

The influence of the introduction of oxygen gas and nitrogen gas into the chamber during deposition on the perpendicular magnetic anisotropy of Gd‐Co amorphous films deposited by ion beam sputtering has been investigated. The films deposited without O2 and N2 addition show perpendicular magnetization in the vicinity of compensation composition. However, the perpendicular anisotropy of them is much smaller than that of the films deposited by rf sputtering. When sputtering ion energy, deposition rate, and Ar pressure are 0.5∼3 keV, 19∼30 A/min, and 8×10−3∼8×10−2 Pa, respectively, the films obtained have almost the same perpendicular anisotropy. On the other hand, the incorporation of oxygen in the films leads to a remarkable increase of perpendicular anisotropy. The films deposited at O2 pressure of 1.6×10−3 Pa have an effective perpendicular anisotropy constant K⊥(K⊥ = Ku‐2πMs2) of about 5×105 erg/cm3, where Ku is 1.1×106 erg/cm3. On the contrary, the incorporation of nitrogen decreases the perpendicular a...

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).