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Notes: The thin films of a magnetoplumbite type of barium (BaM) ferrite have been deposited on SiO2/Si substrates at a rate of 100 A(ring)/min in a gas mixture of 10% O2–90% Ar at a pressure of 2 mTorr by using the facing targets sputtering (FTS) apparatus. They possessed excellent chemical stability and high corrosion resistivity as well as perpendicular anisotropy as large as applicable for perpendicular magnetic recording media. They also seem to be applicable for millimeter wave isolator and circulator. In this study, the saturation magnetization Ms, the coercive force Hc, and the anisotropy field Hk of BaM ferrite films have been controlled by adjusting the rf-bias voltages to substrate Vb during sputtering, where Vb was always negative. The dependencies of Ms and Hc on Vb were shown in Fig. 1. Ms took the maximum value as large as 345 emu/cc at Vb of −30 V and decreased as Vb decreased in the range below −50 V. On the other hand, the perpendicular Hc decreased as Vb increased in the range above −100 V and took the minimum value as low as 910 Oe at Vb of −95 V. Hk and the magnetic anisotropy constant Ku also greatly depended on Vb. Such an apparent Vb dependence of these magnetic characteristics of BaM ferrite films seem to be attributed to the definite change in c-axis orientation of hexagonal crystallite and the different distribution of Fe3+ ions among several occupation sites. These results indicated that the c-axis orientation of BaM ferrite crystallites were promoted by applying proper Vb. Consequently, the bias sputtering technique with FTS method may be useful for preparing the BaM ferrite films composed of the multilayers with different magnetic characteristics, even if only one pair of targets are used without adjusting the other sputtering conditions.

Notes: Uniaxial magnetic anisotropy induced in iron thin films by the oblique incidence of deposition particles was investigated by computer simulation. In the simulation, the self-shadowing effect was considered mainly to explain changes in the magnetic anisotropy of iron films with the incident angle. The simulated grain shape in the film changes significantly with the incident angle of deposition particles. Grains elongated in a direction normal to the incidence direction of depositing particles were clearly observed in simulated film deposited with an incidence angle around 60°. However, the film deposited at an incidence angle of 80° had columnar grains separated from each other and inclined to the incidence direction. Changes in the uniaxial magnetic anisotropy of the film can be qualitatively explained by the shape anisotropy of these grains in the film. The decrease in saturation magnetization of these films with incident angle seems to be mainly caused by the formation of a porous film. © 1996 American Institute of Physics.

Notes: La1−xSrxMnO3 films about 4000 A(ring) thick were deposited on thermally oxidized Si wafers, and then their crystalline orientation and magnetic characteristics were investigated. Orientation of (111) in which large ions such as O2−, La3+, and Sr2+ are most closely packed became preferential with increase of total gas pressure Ptotal and partial oxygen pressure PO2. Although spontaneous magnetization was not detected, even the film deposited at substrate temperature Ts as low as 330 °C revealed obvious orientation of (110) in which metallic ions are most closely packed. The film deposited at Ts of 500 °C, Ptotal of 2.0, and PO2 of 0.1 mTorr, and the film postannealed at 900 °C for 3 h in oxygen atmosphere possessed the saturation magnetization 4πMs of 1.2 and 3.5 kG at 77 K and their Curie temperatures were 217 and 313 K, respectively. B–H curves at 77 K revealed that the easy magnetization direction of these films was in-plane. © 1996 American Institute of Physics.

Notes: Many practical applications using giant magnetoresistance (GMR) have been developed, such as read-out heads and spin valve devices; however, the origin of GMR is not still fully understood. The GMR effect seems to be originated from the spin scattering mechanism whether at the interfaces or at the layer bodies. Therefore, it is necessary to investigate the spin scattering behaviors at the interfaces in GMR multilayers. It is regarded that the mixing and the diffusion of atoms at the interfaces in multilayers can be well promoted by ion bombardment to the interfaces at proper energy in dual ion beam sputtering (DIBS) method. In this study, change of magnetoresistance (MR) and crystallographic characteristics induced by interfacial mixing of atoms were investigated. Specimen films were deposited by DIBS. Additional ion bombardment to the growing surfaces arranges the mixing effect at the interfaces between Ni-Fe and Cu layers. Acceleration voltage of sputtering ion source Vmg were set at 500 V and that of bombarding ion source Vsg was varied in the range of 0–300 V. Si wafers were used as substrates. Ni–Fe/Cu multilayers with GMR were deposited on 50 A(ring) thick Fe buffer layers.Only two monolayers at the interfaces in Ni–Fe/Cu multilayers were exposed to ion bombardment to cause the local interfacial mixing. X-ray diffraction diagrams, showed that (111) orientations of Ni–Fe and Cu crystallites are obtained at Vsg below 200 V and that, on the contrary, (100) orientation became dominant in the films deposited at Vsg above 200 V. There is no apparent differences in MR ratio with increase of Vsg. However, the field sensitivity and saturation field properties were drastically degraded at Vsg above 200 V, while the crystal structure seemed to be changed. These results indicate that spin scattering were mainly occurred at the layer bodies in Ni–Fe/Cu multilayers. These results implied that the interfacial mixing is not so effective for changing MR ratio of Ni–Fe/Cu multilayers. However, the behavior of magnetization vectors are much influenced by change of local structure at the interfaces. These results seem to confirm the proposed theory; i.e., the spin scattering in layer bodies is the dominant mechanism on GMR in Ni–Fe/Cu multilayers. © 1996 American Institute of Physics.

Notes: Fe/Al multilayers have been prepared by the ion beam sputtering method with use of Ar and Kr as the working gas. Sputtering by Kr ion beam deposited the multilayer with better crystallinity, smaller interdiffusion between layers, and lower electrical resistivity than sputtering by Ar ion beam. Multilayers with thicknesses of Fe and Al layers of 50–120 A(ring) and 15–20 A(ring), respectively, possessed excellent soft magnetism. Such soft magnetism seems to be related, in part, to the fine granulation in Fe layers.

Notes: A new type of recording head for a perpendicular magnetic recording system, a dual track complimentary (DTC) type of thin-film head, was proposed in this study. The magnetic core of the head has a "U'' character shape which is provided with "a pair of'' recording tracks and the efficiency to detect flux reversal in the media will become high enough to achieve high linear density. The two-dimensional analysis of DTC heads implied that the perpendicular component of the head field should become larger by using the double-layered media under a narrower spacing condition. Recording characteristics using conventional ring head were evaluated in order to determine the principle of DTC configuration. Several DTC heads were prepared using photolithography technique and their performances were examined. A typical DTC head has inductance of about 500 nH, which is relatively low, and constant up to 10 MHz. DTC heads seems to be one of the most hopeful candidates as the heads useful for perpendicular magnetic recording systems. © 1996 American Institute of Physics.

Notes: Ba ferrite films were deposited in a mixture of Xe, Ar, and O2 by using facing targets sputtering apparatus with sintered targets of Fe-excessive BaM ferrite. By using Xe as sputtering gas, the bombardment of energetic Ar atoms recoiled from target to film surface was sufficiently suppressed and Fe content in Ba ferrite crystallites was significantly increased. It was found that the segregation of spinel crystallites among BaM ones were not observed and these BaM crystallites revealed the excellent c-axis orientation normal to film plane and clear perpendicular magnetic anisotropy. At substrate temperature Ts of 600 °C, saturation magnetization 4πMs of 5.1 kG, which is larger than that of BaM ferrite single crystal, and perpendicular coercivity Hc⊥ of 2.4 kOe were obtained. BaM ferrite films composed of well c-axis oriented crystallites with large perpendicular magnetic anisotropy constant, large saturation magnetization 4πMs of 4.7 kG and high perpendicular coercivity Hc⊥ of 2.4 kOe were obtained at substrate temperature Ts as low as 475 °C. © 1996 American Institute of Physics.

Notes: For Tb-Fe-Co(MO)/Al bilayered films, dependence of perpendicular magnetic anisotropy constant Ku⊥ on MO layer thickness tMO of 3–300 nm and Al layer thickness tAl of 5 and 100 nm has been investigated. For either tAl, easy magnetization direction was normal to film plane at tMO above 4 nm. Ku⊥ of films with tAl of 5 nm increased drastically with increasing tMO for tMO〈10 nm and then assumed a constant value of 4×106 erg/cm3 which is two times larger than that with tAl of 100 nm. This difference in Ku⊥ between them may be attributed to stress induced anisotropy. Estimation of rotational hysteresis loss Wr and its integral R suggests that the mechanism of magnetization reversal may be attributed to incoherent curling mode. © 1996 American Institute of Physics.

Notes: Co-Zn ferrite films with small grains for magnetic recording media at ultrahigh density were deposited "plasma free'' on a substrate by using the dc facing targets sputtering apparatus without subsequent annealing process. The films deposited at a substrate temperature Ts as low as 90 °C were composed of crystallites with excellent (111) orientation and exhibited a saturation magnetization 4πMs of 3.3 kG and an in-plane and perpendicular coercivity Hc(parallel) and Hc⊥ of 1.8 and 2.2 kOe, respectively. The films deposited at a Ts of 250 °C exhibited 4πMs of 4.8 kG and possessed almost the same Hc(parallel) and Hc⊥ of 1.5 kOe.

Notes: Fe films have been deposited by ion beam sputtering using Ar, Kr, and Xe gases. The sputtering voltage VS was varied in the range of 900–1800 V. The magnetic properties of the films had the significant relationship with the element of the sputtering gas. The saturation magnetization 4πMS was 21 kG for Ar and 20 kG for Kr or Xe. The coercivity HC took the minimum value of 5 Oe at VS of 1200 V for Ar. The energy/the number of the energetic particles, such as the sputtered atoms and the recoiled ions bombarding to the substrate was calculated by Monte-Carlo simulation in the sputtering system with an amorphous Fe target. The average energy of the sputtered atoms ES was 40–60 eV for Ar, 30–34 eV for Kr and 24–34 eV for Xe. The average energy of the recoiled ions ER was 200–370 eV for Ar, 60–100 eV for Kr, and 25–50 eV for Xe. The energy was remarkably different among their sputtering gases with different atomic mass. The bombardment by the recoiled ions at the high energy reduced the coercivity HC of the Fe films. © 1998 American Institute of Physics.