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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: It seemed to be possible to distort the Fe crystal lattice in Fe/Mn multilayers, because the atomic radii of α-Fe and α-Mn with cubic crystal lattice are 1.26 and 1.29 A(ring), respectively. It is very interesting to investigate how crystallographic and magnetic characteristics of the Fe/Mn multilayers were changed by modulating the thickness of Fe and Mn layers. In this study, 2000-A(ring)-thick Fe/Mn multilayers with sharp periodicity were deposited on plasma-free substrate Si wafer by the facing target sputtering method. The Ar gas pressure pAr was set at 2 mTorr. Deposition rates of Fe and Mn layers were 5 and 2 A(ring)/s, respectively. The thicknesses of Fe and Mn, δFe and δMn, were in the range of 20–200 A(ring) and 5–100 A(ring), respectively. The crystallites in Fe and Mn layers revealed the distinct orientation of α-Fe(110) and α-Mn(411) planes, respectively. The Fe(110) interplanar distance dFe increases from value close to Mn(411) interplanar distance dMn to that close to dFe with increase of the Fe layer thickness δFe in the range of 10–100 A(ring). The distortion of Fe crystal lattice increased with decrease of δFe and increase of interface number. The difference between the saturation magnetization 4πMs measured for the specimen multilayers and that calculated for the single layer films of simply diluted alloy increased with increase of δFe. However, 4πMs of the Fe layers in Fe/Mn multilayers did not changed with δMn except for the films with δFe as extremely small as 20 A(ring). And 4πMs took the value of nearly zero at δFe of 10 A(ring). In the range of δMn of 20–50 A(ring), the Fe lattice distortion was most remarkable and the coercivity Hc increased highly due to the large in-plane uniaxial anisotropy. Hc took its maximum value of about 70 Oe at δFe and δMn of 50 A(ring). This result may imply that the distortion of both layers are most remarkable. Consequently, it was confirmed that dFe and the crystallite size in Fe layers were changed and Hc was modified by modulating both δFe and δMn.

Notes: Ferrimagnetic Mn4N films have been successfully prepared at low process temperatures using the facing targets sputtering apparatus. The mixture gas of Ar and N2 with the ratio of N2 in pressure to total gas RN2 of 10% was optimal as the reactive working gas for depositing Mn4N films, since the deposition at excessive RN2 tended to cause the formation of Mn3N2 crystallites. In fact, they appeared in films deposited at RN2 higher than 30%. The film deposited at the substrate temperature Ts of 200 °C exhibited saturation magnetization 4πMs of about 300 G. The films prepared at Ts of 350 °C exhibited 4πMs and an in-plane coercivity Hc(parallel) of 450 G and 300 Oe, respectively. The films annealed at 400 °C in vacuum furnace exhibited 4πMs larger than about 510 G. However, the film annealed at temperature above 500 °C exhibited 4πMs smaller than 80 G.

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.

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: Multilayers composed of 30 [Ni–Fe/Cu] bilayers deposited on a 50-A(ring)-thick Fe buffer layer were prepared by ion beam sputtering. The magnetoresistance (MR) ratio Δρ/ρ0 of the multilayers took high value at the Cu layer thickness δCu of 10, 20, and 32 A(ring) for the multilayers with Ni–Fe layer thickness δNi–Fe of 10 A(ring). It was observed that (100) orientation of Ni–Fe and Cu crystallites were enhanced at δCu of 20 and 32 A(ring). The multilayered film with δCu of 10 A(ring) exhibited Δρ/ρ0 as high as 12%. The multilayered film possessed good soft magnetic properties, and exhibited coercivity Hc and relative permeability μr of about 4 Oe and 800, respectively. The saturation magnetic field Hs was about 300 Oe. Δρ/ρ0, Hc, and Hs at δCu of 20 A(ring), i.e., at the "second peak,'' were 6%, 10 Oe, and 25 Oe, respectively. The δCu dependence of Δρ/ρ0 seemed to be correspondent to that of the preferential orientation of the (100) plane. Ni–Fe/Cu multilayers with the same construction but without an Fe buffer layer did not reveal apparent (100) preferential orientation and did not exhibit Δρ/ρ0 as high as detectable. Then, Δρ/ρ0 was strongly dependent not only on interlayer thickness, such as δCu, but also (100) crystallite orientation.

Notes: Fe-Zr sputtered thin films with large perpendicular magnetic anisotropy were prepared by facing targets sputtering (FTS) apparatus. Perpendicular anisotropy was clearly observed at Zr content around 10 at. %. The substrate temperature Tsub of ∼100 °C resulted in the large perpendicular magnetic anisotropy energy Ku of 1.2 × 106 erg/cc and the high perpendicular coercivity Hc⊥ of 1.0 kOe in the Fe-Zr sputtered film with the saturation magnetization 4πMs of 6.7 kG. It was also shown that Tsub higher than 200 °C caused the decline of Ku and the lowering of 4πMs. It is concluded that Fe-Zr sputtered film may be applicable for the media in the perpendicular magnetic recording system.

Notes: Fe/Ti multilayered films prepared by plasma-free sputtering revealed high coercivity. The effect of elevating substrate temperature and adding Zr and Cr into Fe and Ti layers, respectively, have been examined to increase the coercivity Hc. The elevation of substrate temperature to 200–400 °C did not bring a significant increase in Hc. Addition of Zr into Fe layers caused a soft magnetism because of the small Fe grain size. On the other hand, addition of Cr into Ti layers revealed a significant increase in Hc especially for the films with small Fe thickness lFe. Although the magnetization of Fe/Ti multilayered films with lFe of about 16 A(ring) was almost zero, that of Fe layers in Fe/Ti90Cr10 multilayered films was as large as 14 kG with a high Hc of about 400 Oe. X-ray diffractometry (XRD) implies that the small Fe grain size and the magnetic interaction between atoms at the interface may be one of the origins of such high Hc.

Notes: Co/Cu multilayers deposited on an amorphous Si (a-Si) buffer layer revealed good crystallinity and lower resistivity than ones deposited on other buffer layers. The periodicity and the sharpness at the interface between each layer were not as good as those in the multilayer with a Ni–Fe buffer. Therefore, the multilayer with a Si buffer exhibited smaller resistivity ρ but slightly smaller change of resistivity Δρ. The annealing process improved the periodicity and the sharpness at the interface in the Co/Cu multilayer with a Si buffer, and the value of the magnetoresistance ratio in the multilayer with a Si buffer (17.1%) became larger than that with Ni–Fe (15.5%). © 2000 American Institute of Physics.