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Notes: The intermittent deposition technique using 10-nm-thick Cr unit layers was performed to improve structural and magnetic characteristics of the Co–Cr–Ta recording layer deposited on the Cr underlayers. The Cr layers were composed of 10-nm-thick Cr unit layers intermittently deposited at intervals of 3 min or with N2 flow for 10 s between the depositions of each unit layer, in order to prevent the growth of Cr crystallites. The intermittent deposition of the Cr underlayers decreased in crystallite size 〈D〉Cr(200) and increased the coercivity Hc of the Co–Cr–Ta recording layer. N2 flow degraded the crystalinity of the Cr underlayer and decreased Hc(parallel) of the recording layer. © 2000 American Institute of Physics.

Notes: A magnetoplumbite type of Ba ferrite (BaM) thin layer was deposited on a 9 nm thick Pt underlayer, and excellent c-axis orientation was observed even for an 8 nm thick BaM layer, which corresponds to only three or four BaM unit cells. The grain size was almost in the same range of 60–85 nm even when the BaM layer thickness tBaM decreased from 60 to 17 nm, and tBaM should be reduced below 10 nm to make a grain size smaller than 50 nm. However, the perpendicular coercivity Hc⊥ and squareness S⊥ decreased drastically from 2.6 to 0.5 kOe and from 0.6 to 0.2, respectively, with the decrease of tBaM from 60 to 8 nm because of higher demagnetizing field and susceptibility to thermal fluctuation. On the other hand, the [BaM(5–24 nm)/Pt(9 nm)]3 multilayer exhibited higher Hc⊥ and larger S⊥ than the BaM/Pt bilayer for the same BaM layer thickness and Hc⊥ and S⊥ of the [BaM(8 nm)/Pt(9 nm)]3 multilayer was 2.0 kOe and 0.6, respectively. It was clarified that the deposition of the BaM/Pt multilayer was very effective for achieving a high perpendicular magnetic anisotropy constant even for the ultrathin BaM layer. © 2001 American Institute of Physics.

Notes: It has become attractive to prepare films of transition metal nitride for both the studies of ferrimagnetism and their practical applications. Mn4N is well known as one of the typical ferrimagnetic materials with an effective moment of Bohr magnetons of 1.0–1.2 μB per unit cell. However, high temperature processing is required to synthesis such materials. We have succeeded in depositing Mn4N films at a relatively low substrate temperature Ts of around 300°C by reactive facing target sputtering (r-FTS).1 In this study, Al and Cu underlayers were deposited to enhance the epitaxial effect between (111) preferred texture in such layers and the (111) texture of Mn4N crystallites in order to deposit Mn4N films with better crystallinity at lower Ts. Mn4N films were deposited on Si wafer substrates by sputtering a pair of sintered Mn disks in a mixture of Ar and N2 gases. Total gas pressure was set at 2 mTorr and the ratio in pressure of N2 gas to the RN2 mixture ranged from 0% to 40%. Ts was varied in the range of 40–400°C. Al and Cu layers with thicknesses of about 500 Å were used as underlayers. Mn–N films with (111) oriented Mn4N crystallites could be prepared at RN2 of 10% and Ts above 270°C. Those films revealed the saturation magnetization 4πMs of about k40 emu/cc. Excessive RN2 and Ts above 400°C caused the formation of another phase nitride, such as Mn3N2, which caused the degradation of 4πMs. Basically, Mn atoms in Mn4N crystallites form fcc lattices. Since Al and Cu atoms form fcc lattices and their lattice constant is almost the same as that of Mn4N, Al and Cu thin layers were used as underlayers. Substrate biasing of about −160 and −70 V during deposition of Al and Cu layers, respectively, was very effective in attaining (111) orientation in those films. Mn nitride films deposited at Ts as low as about 200°C on (111) oriented Al underlayers were composed of (111) oriented Mn4N crystallites which revealed 4πMs of about 24 emu/cc at room temperature. (111) oriented Cu layers were not as effective in depositing Mn4N films at low Ts. Consequently, Al underlayers were suitable to deposit films composed of (111) oriented Mn4N crystallites at low Ts of around 200°C. ©1997 American Institute of Physics.

Notes: Ba-ferrite (BaM) thin films were prepared by both a facing targets sputtering (FTS) system and dc magnetron sputtering (DCMS) at room temperature. They were successively annealed to crystallize. The films prepared by FTS system were crystallized at 650 °C, while those prepared by DCMS system were crystallized at 700 °C. Saturation magnetization, coercivity, and squareness ratio of the films prepared by FTS are 210 emu/cc, 3.3 kOe, and 0.7 in perpendicular direction, respectively, after the annealing at 650 °C. It was found that oxidized Fe is partially reduced to metallic Fe by high-temperature annealing. © 1996 American Institute of Physics.

Notes: Fe/Ta multilayered films were deposited on Si substrates by ion beam sputtering (IBS) by alternately using separate Fe and Ta targets. Thickness of Fe and Ta layers lFe and lTa bilayers lFe+lTa in specimen films and total thickness of multilayers films with 10 bilayers were constant at 100 and 1000 A(ring), respectively. For as-deposited films, coercivity Hc took minimum value of 0.15 Oe at lFe of 88 A(ring) and lTa of 12 A(ring), where saturation magnetization 4πMs was 18.3 kG. Films postannealed at 500 °C exhibited 4πMs of 19.1 kG, Hc of 0.05 Oe and μr of 1820. Fe:N/Ta:N multilayered films with N content of ∼10 at. % were deposited by bombarding N ions extracted from the subgun while the films were being grown. For as-deposited films, Hc took minimum value of 0.07 Oe and μr took maximum value of 1310 at lFe:N of 93 A(ring) and lTa:N of 7 A(ring), where 4πMs was 20.5 kG. Films postannealed at 500 °C exhibited 4πMs of 21.2 kG, Hc of 0.03 Oe and μr of 2380. Consequently, Fe/Ta and Fe:N/Ta:N multilayered films may be very suitable for magnetic cores in inductive heads for ultrahigh density recording. © 1996 American Institute of Physics.

Notes: The addition of Ta and N into sputtered Fe90Co10 alloy films was performed to attain soft magnetism with large saturation magnetization 4πMs. Addition of Ta below 8 at. % to Fe90Co10 films improved their crystallinity and the lattice constant of Fe crystallites was expanded. These films revealed relatively large 4πMs of about 21 kG. The deposition of Fe–Co and Fe–Co–Ta films at N2 partial pressure PN2 below 0.1 m Torr was so effective as to cause fine granulation in the film. Fe84.6Co8.4Ta7:N films deposited at PN2 of about 0.2 mTorr and postannealed at 150 °C revealed 4πMs and relative permeability μr of about 16 kG and 1500, respectively. © 1996 American Institute of Physics.

Notes: Amorphous Tb-Fe-Co single layers and Tb-Fe-Co/M (M: Ta, C, Co82Cr18, Ni81Fe19) bilayers have been prepared by using a facing targets sputtering apparatus. The Tb-Fe-Co films deposited by Kr sputtering exhibited internal stress as low as 1×109 dyn/cm2 even at a pressure as low as 0.2 mTorr. The Tb-Fe-Co/Ta bilayers showed a Kerr rotation angle as large as 0.85° at the thickness of Tb-Fe-Co layer of about 30 nm. The direction of magnetic moments in Tb-Fe-Co layers were arranged antiparallel by a soft magnetic Ni81Fe19 overlayer.

Notes: Pb-substituted Ba-ferrite films were prepared at various substrate temperature Ts by dc magnetron sputtering and their crystallographic characteristics and magnetic properties were investigated. The substitution of Pb facilitates the crystallization and improves the crystallinity for hexagonal M phase. All of the films prepared at Ts above 460 °C exhibit a good c-axis orientation and the c-axis dispersion angle (Δθ50) for Pb-substituted Ba-ferrite films is as small as 1°. The coercivities (Hc⊥) and Hc(parallel)) and saturation magnetization Ms of Pb-substituted Ba-ferrite films are 0.7–1.0 kOe, 0.2 kOe and 250–300 emu/cm3, respectively.

Notes: A perpendicular magnetic recording tape requires a high magnetic anisotropy field Hk and a small distribution of the perpendicular magnetic anisotropy field σhk/Hk. It can be expected that by the extension of the interplane distance of (002) plane d(002) in Co-Cr, a perpendicular magnetic anisotropy energy will be increased and Hk becomes higher. It can be also expected that the σhk/Hk becomes smaller by the improvement of the crystallinity of Co-Cr film. Therefore, in order to achieve the above, the following experiments were attempted. At first, a small amount of Ta was added to Co-Cr. This, as a result, extended the d(002) of the Co-Cr from 2.033 to 2.046 A(ring). Consequently, Hk was increased from 4.4 to 5.1 kOe and σhk/Hk was reduced from 0.14 to 0.11. Second, as a sputtering gas, Kr gas was used instead of Ar gas. The use of Kr resulted in greater crystallinity in the film, increasing the peak intensity I(002) of x-ray diffraction of the Co-Cr-Ta from 2090 to 2500 cps. Consequently, σhk/Hk was reduced up to 0.07. Last, a recording and reproducing experiment with the Co-Cr-Ta tape was attempted with the use of a hilical-scan VTR machine. As a result, a reproduced output of 56 nVO-P (μm T m/s) was obtained at the recording wavelength of 0.33 μm. This figure is equivalent to the output at the recording wavelength of 0.66 μm of metal-powder tape.

Notes: Although the as-deposited Fe–Co–Ta:N single layer films with a thickness of 200 nm possessed large 4πMs of about 16 kG, they revealed low μr. [Fe–Co–Ta:N/Ti]n multilayers were prepared with the aim to improve soft magnetic characteristics of Fe–Co–Ta:N films. The [Fe–Co–Ta:N(50 nm)/Ti(10 nm)]4 multilayered films exhibited relatively high μr of about 400 even in the as-deposited state. Furthermore, they exhibited better thermal stability of their soft magnetism. For example, the multilayered films postannealed at TA of about 300 °C lost only 20% of their moment, compared to as-deposited films, and maintained a relatively high μr. By contrast, a Fe–Co–Ta:N(200 nm) single layer film lost, at the same temperature, nearly 50% of its moment. X-ray diffractometry indicates that the postannealed multilayered films did not include such paramagnetic ζ-Fe2N crystallites. It seemed that the Ti insertion layers worked as barrier layer for N diffusion to prevent the formation of such nitride crystallites. © 1997 American Institute of Physics.