ITE Technical Report
Online ISSN : 2424-1970
Print ISSN : 1342-6893
ISSN-L : 1342-6893
23.68
Showing 1-18 articles out of 18 articles from the selected issue
  • Type: Cover
    Pages Cover1-
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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  • Type: Index
    Pages Toc1-
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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  • K.J. Lee, T.D. Lee
    Type: Article
    Session ID: VIR99-75
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Role of the nucleation field in perpendicular magnetic recording was studied using micromagnetic and Monte Carlo calculations. Three different types of perpendicular media with the same grain size of 7.5nm and the same value of KV/kT of 37 but with different K value have been assumed. The three types of media showed different nucleation field in hysteresis loops. A large nucleation field resulted from smaller h_m and large h_e. If the nucleation field was large enough to resist the trail field of head, reverse domain was not formed in the bit. Therefore, the medium noise was significantly reduced in that case. SNR increased in this type of media with increasing exchange parameter. The increase of SNR is related to decreased noise rather than increased signal with increasing the exchange parameter. The main source of noise seems to be DC erase noise not transition noise. In the point of view of media, areal recording density of 90 Gbit/inch^2(564kfci×160ktpi)would be attainable in perpendicular recording with single magnetic layer and ring type head when the medium has a large nucleation field. To realize these, however, there should be improvement of writing head because of limitation of head leakage field in a narrow gap head.
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  • Atsushi Sato, Shigeki Nakagawa, Masahiko Naoe
    Type: Article
    Session ID: VIR99-76
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Ferromagnetic Co_<77>Cr_<20>Ta_3 layer were deposited on a Pt seed layer by a facing targets sputtering apparatus. The c-axis orientation of the Co-Cr-Ta and Pt crystallites revealed better at the substrate temperature T_S above 200℃. Relatively high perpendicular coercivity H_<C&bottom;>of 2.5kOe was obtained for the bilayered film with the thickness of Co-Cr-Ta layer, δ_<Co> of 50nm deposited at T_S of 250℃. Measurement of the anomalous Hall voltage clarified that the bilayered film with δ_<Co> of 30nm revealed larger perpendicular magnetization than the single layer. The Pt seed layer is effective to deposit ultra-thin ferromagnetic Co-Cr-Ta layers.
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  • Nobuyuki Inaba, Masaaki Futamoto
    Type: Article
    Session ID: VIR99-77
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Magnetic layer thickness dependences of magnetic properties are investigated for Co-Cr-Pt polycrystalline thin films with different Cr-alloy underlayers(Cr-Ti, Cr-W, Cr-Mo, Cr-V, Cr-Mo-V). The specimens with Cr-Ti, Cr-V, and Cr-Mo-V underlayers show higher coercivities by about 30% and lower activation magnetic moments than those with Cr-Mo underlayer. The effective diameter of activation volume increases by 10-20% when the magnetic layer thickness is decreased from 12 to 8 nm. Temperature dependences of magnetic properties are also determined and discussed by reffering to the data obtained using single crystal magnetic thin films with similar composition.
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  • Ding JIN, Ying Su, Jian Ping WANG, Hao Gong
    Type: Article
    Session ID: VIR99-78
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Post-annealing treatment for CoCrPt magnetic thin films were tried in different thermal conditions, by changing the time annealing procedure. Coercivity(H_c)improvement was achieved in every annealed sample compared with those as deposited, in which as high as 5210 Oe has been attained. In order to clarify the mechanism of this annealing treatment on the magnetic properties, x-ray diffraction(XRD)spectrums combined with the magnetic properties were carefully studied. Co and Cr lattice parameters were separately calculated from different crystal lattice plane. It was found that a axis lattice spacing of Co haxagonal structure also increases monotonically with increased annealing time. Simultaneously, c axis lattice did have any obvious trend. Variation of Co hcp peaks significance may due Cr or Pt atom substitution of Co atoms in the Co-rich grain cores. Combined with the analysis of Co-rich grain size by X-ray diffraction peak broaden width, which was not very consistent with the result obtained from other's TEM and AFM studies, Cr diffusion was suggested to be the governing factor at short annealing time region. Co-rich grain growth should also be applied to explain the variation of magnetic properties in longer post annealing.
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  • Ding JIN, Jian Ping Wang, Qionghui Han, Hao Gong
    Type: Article
    Session ID: VIR99-79
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In order to optimize the magnetic recording properties for CoCrPt recording thin film media, different Mo and W doping CoCrPt based magnetic thin films were fabricated by using DC magnetron sputtering method. It was observed that Mo and W doping could increase the coercivity(H_c), at the same time maintain lower Pt content. Sole W doping showed no apparent trend of enhancing the coercivity by rising the Mo contents. For samples with less W or Mo doping, the saturation magnetization(M_S)value increased significantly when we tried to further doping. This trend was preserved for different working pressure. But for samples with higher W or Mo contents, M_S is unlikely to change much. It suggested that doping atoms may easily penetrate into Co rich grain core area and help Cr atom reset at the grain boundary. Evidences from X-ray diffraction study showed that lattice constants of Co were varied by more Mo doping. On the other hand, coercive squareness(S^*)studies found that moderate W content doping, may have less exchange coupling.
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  • H. Wang, S.P. Wong, W.Y. Cheung, N. Ke, M.F. Chiah, H. Liu, X.X. Zhang
    Type: Article
    Session ID: VIR99-80
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Granular Co_xC_<1-x>(x=60, 65, 70 at.%)films were prepared by pulsed filtered vacuum arc deposition. Subsequent thermal annealing was performed in vacuum at various temperatures. The films were characterized by non-Rutherford backscattering spectrometry, Raman Spectroscopy, atomic force microscopy and magnetic force microscopy. Clear magnetic force microscopy images were only observed in the films after annealing at a sufficiently high temperature, indicating that there was perpendicular magnetic anisortropy in these films. The M-H hysteresis loops of the films were measured by a SQUID magnetometer. The optimum annealing temperature for the maximum coercivity was found to depend on the cobalt concentration. For a typical Co_<65>C_<35>sample of 20nm thick after annealing at 350℃ in vacuum for 1 hour, the saturation magnetization was 500 emu/cm^3, the coercivity was 460 Oe, and the ratio of the remanence to the saturation magnetization was 0.68 at 300K.
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  • Ding JIN, Jian Ping Wang, Hao Gong
    Type: Article
    Session ID: VIR99-81
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    To explore the role of the interface between underlayer and magnetic layer in Co alloy based media for ultra high recording density, two series of thin films with very thin intermediate layers were made. CrTi and CoCrPtTa were chosen for intermediate layer material as opposite extremes in terms of crystal lattice. The coercivity varied in a very broad range with the changing of working pressure for the intermediate layer while maintaining other sputtering condition. The pressure dependence for magnetic coercivity was quite different for these two kind of intermediate layer materials. Those films with CrTi intermediate layers showed abnormal periodical drops for coercivity value. It suggested that the different interface condition influence the epitaxy growth and hence magnetic properties by two ways:affecting on the grain boundary formation and stress related lattice variation.
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  • Dian JIN, Jian Ping Wang, Hao Gong
    Type: Article
    Session ID: VIR99-82
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Using substrate bias configuration, triple CoCrPt layer magnetic thin films were deposited by DC magnetron sputtering on CrV and glass substrate. Coercivity showed an increase for films with bias sputtered CoCrPt layer in which coercivity(H_C)was optimized for NB-B-NB type film deposited at higher temperature(300℃)(NB:no bias and B:bias applied in sputtering). Size reduction of the magnetic domains was observed by Magnetic Force Microscope. On the other hand, Secondary Ion Mass Spectroscopy study found no remarkable composition variance for Co and Cr element in depth scale. Crystal grain morphology and structure was studied by transmission electron microscope. Bias-sputtering-caused defects, slight composition changes and interfacial diffusion were discussed to explain the improvement of magnetic properties.
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  • M. Abe, Y. Kitamoto
    Type: Article
    Session ID: VIR99-83
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    For applying to perpendicular magnetic recording, ferrite films are prepared by ferrite plating from an aqueous solution at 85-90℃;Co-ferrite films for recording media and NiZn ferrite films for high permeability underlayers. The Co-ferrite films have a prominent perpendicular magnetic anisotropy, exhibiting excellent magnetic hysteresis loops with Hc=〜3200Oe. This paper describes improvement of magnetic properties of the ferrite films by optimizing plating conditions, and reports preliminary results of signal retrival performed on the Co-ferrite films.
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  • Hyuk Lim, Se-Young Choi, Young-Jei Oh
    Type: Article
    Session ID: VIR99-84
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Co-ferrite thin films on Corning glass substrate have been fabricated by a chelating sol-gel process. Structural and magnetic properties of films have been studies as a function of annealing temperature with a X-ray diffraction and vibrating sample magnetometer. XRD result show most of Co-ferrite grains are oriented in randomly. Rapid annealing(RA)and Annealing processes were used for the variation of heat treatment and characteristic comparison. Coercivity were changed with thermal condition and magnetization were increased as a function of soaking time. With pronged soaking time, however, it was decreased due to the diffusion of cations from glass substrate by XPS analysis. RA process in preparation of Co-ferrite thin films was effective way to prevent inter-diffusion at interfaces and to form a single phase in reduced soaking time. And also YSZ(yttria stabilized zirconia)buffer layer between Co-ferrite and substrate was more effective to improve magnetic properties of the films at higher temperature. It was observed that Co-ferrite thin films have grain like feature typically 35nm size and their rms roughness is about 1.3nm. The saturation magnetization of the 900℃ 150 sec rapid annealed thin films was 400 emu/cm^3 and the coercivity of the film was about 3000 Oe.
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  • Xiaoxi Liu, Jiammin Bai, Fulin Wei, Zheng Yang, Shigeto Takei, Akimits ...
    Type: Article
    Session ID: VIR99-85
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Hexagonal Strontium ferrite thin films were prepared by post-annealing process onto Al_2O_3, SiO_2, ZnO underlayer. The effects of those underlayers were discussed. It is found that SiO_2 underlayer is effective to prevent the reaction between the film and the substrate. Steps were found in the hysteresis of film grown on the Al_2O_3 underlayer indicate the existence of two magnetic phases. The effects of the annealing temperature and the thickness of the underlayer have also been discussed.
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  • Xiaoxi Liu, Jianmin Bai, Fulin Wei, Zheng Yang, Kazu Ito, Akimitsu Mor ...
    Type: Article
    Session ID: VIR99-86
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    BaM films with various compositions were prepared by alternate deposition the films from two targets with different composition. The effects of Ba content on the c-axis orientation, temperature dependence of the magnetic properties and the microstructure of the films were investigated. Our results show films with high Ba content tends to have c-axis normal to the film plane orientation, and a large value of dH_c/dT due to the plate-like grains. While films with low Ba content tends to have c-axis in the film plane orientation, and a small value of dH_c/dT caused by the aciculate shaped grains.
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  • J. Feng, N. Funabashi, N. Matsushita, S. Nakagawa, M. Naoe
    Type: Article
    Session ID: VIR99-87
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this study, SiO_2 added Ba ferrite(BaM:SiO_2)films were prepared. BaM:SiO_2 films exhibited H_<c*&boiiom;>as high as 4.2kOe and squareness ratio of 0.83, although M_S decreased to 80% of that of simple Ba ferrite films. Angular dependence of coercivity H_C and remanent coercivity H_r were investigated to explain the magnetization reversal mechanism. Intergranular interctions in the films were also evaluated. The magnetization reversal mode of Ba ferrite films with and without SiO_2 additives is not coherent rotation but seems like curling mode. SiO_2 additives did not decrease perpendicular anisotropy of grains apparently, but seemed to prevent the expansion of reversed domain in the magnetization reversal process of curling just like some effects of pinning.
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  • Dongping Wu, Tian Xie, Fulin Wei, Mitsunori Matsumoto, Zheng Yang
    Type: Article
    Session ID: VIR99-88
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    M-type Strontium ferrite thin films were prepared in the mixture gases of Ar and O_2, using DC magnetron sputtering apparatus. The effects of target composition on structure and magnetic properties of the films were investigated. It is found that the films show c-axis orientation normal to the film plane, and the orientation factor(fc)has little change as the coefficient n of target composition SrO・nFe_2O_3 increases. The saturation magnetization Ms and corecivity Hc of the films have largest value of 321emu/cc and 3.4kOe at n=4, then reach a state value of 250emu/cc and 2.2kOe with the increase of coefficient n, respectively. It indicates that the composition of the films deviates from that of the target. The film prepared by the target composition of SrO・4Fe_2O_3 approaches to the stoichiometric M-type hexagonal strontium ferrite and exhibits best hard magnetism.
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  • Jiammin Bai, Xiaoxi Liu, Fulin Wei, Zheng Yang, Mitsunori Matsumoto
    Type: Article
    Session ID: VIR99-89
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In order to investigate the effects of the substitution on the magnetic properties of the samples, the La-Zn substituted SrM ferrite La_XSr_<1-X>Zn_XFe_<12-X>O_<19>(x=0-0.6)fine particles were prepared. It is observed that the M_s as well as K_1 increased, with increasing substitution rate, up to a maximum for about x=0.3, then decreased rapidly. A qualitative explanation was given to account for this phenomenon. And the value of dH_c/dT also reduced rapidly with the increase of x.
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  • Type: Appendix
    Pages App1-
    Published: November 09, 1999
    Released: June 23, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
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