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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: Successive growth of Ba-ferrite (BaM) layer on YBa2Cu3Ox (YBCO) layer has succeeded by using facing targets sputtering (FTS) method, which is suitable for preparing oxide films. BaM layer deposited on YBCO showed clear c-axis orientation of their crystallites normal to the film plane and they could be grown successively without interdiffusion. These bilayered films showed apparent perpendicular magnetic anisotropy originated from BaM layer. Preferred c-axis orientation in BaM layer could be clearly observed when its thickness was as small as 300 A(ring).

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: 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: In this study, magnetization reversal of a Co–Cr very thin film with rectangular area of 1.0×1.0 cm2 was observed by means of the anomalous Hall effect. The amplitude of the Hall voltage VH took the maximum and minimum values when magnetic field was applied perpendicular and parallel to the film plane, respectively. The hysteresis loop observed in perpendicular direction exhibited the largest lean for the film deposited at substrate temperature Ts of 100 °C. It was found that for the film with a large perpendicular magnetic anisotropy constant, VH is independent to the angle of applied field. The Hall loop of the Co–Cr film 150 Å thick revealed its shape more similar to a Kerr loop than a vibrating sample magnetometer loop. The VH–H measurement is useful to evaluate the magnetization process of very thin films without the perturbation of the magnetization component from the substrates and the specimen folder in the measurement system especially for the case of obliquely applied magnetic field condition. © 1999 American Institute of Physics.

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: 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.