日本応用磁気学会誌
Online ISSN : 1880-4004
Print ISSN : 0285-0192
ISSN-L : 0285-0192
20 巻 , S_1_MORIS_96 号
選択された号の論文の98件中1~50を表示しています
Key Talks
M-O Effects
High Density Recording
High Density Recording
M-O Effects
Magnetism
  • M. Guillot, H.Le Gall, J. Gouzerh, J.M. Desvignes, M. Artinian
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_161-164
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      At λ= 633 nm, very accurate measurements of the Faraday rotation on epitaxial garnet films of the composition {R3-xBix}[Fe2](Fe3)O12 with R = Dy, Y and high Bi content (x ≅ 1.30) are reported, in the temperature range 10 -620 K under magnetic field up to 20 kOe applied along the [111] direction. The analysis of the data in terms of the sublattice magnetization reveals, at low temperatures, a large contribution of the rare earth {c } sublattice induced by the Bi substitution. This enhancement of the "electric" dipole Faraday rotation is strongly temperature dependent and vanishes at room temperature. This result is compared with that observed for the same Bi-substituted rare earth iron garnets in the near infra-red band.
  • JAI-YOUNG KIM, IN-OH HWANG, HYEON-CHANG HONG, DONG-HO SHIN
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_165-168
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      Amorphous NdTbFeCo alloys are prepared with different substrate positions and rotation speeds of substrate holder to investigate the effect of magnetic properties on Kerr rotation angle. Angular momentum of the substrate holder induces high squareness of magnetic hysteresis loops in the amorphous alloys. This leads to the fact that the magneto static energy of the hysteresis loops is proportional to remanent Kerr rotation angles.
  • M. Kratzer, S. Becker, H. Rohrmann, K. Röll
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_169-172
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      RE/TM films used for magneto-optical (MO) data storage are commonly covered with reactively sputtered SiN protective layers. For stoichiometric Si3N4 cover layers no reaction between the magnetic and the protective layer is expected. But if there is a surplus of nitrogen within the protective layer the magnetic properties and the long-term stability of the magnetic layer may be influenced.
    To investigate this we prepared ferrimagnetic TbFeCo-films covered with a SiN protective layer containing a surplus of nitrogen. For testing their long-term stability the films were annealed several times. To analyze the magnetic properties measurements of Kerr hysteresis were performed. The magnetic anisotropy was measured by Kerr Torque Magnetometry, a very sensitive magneto-optical method which provides local information about the anisotropy field at the surface region of the magnetic layer.
    As a result substantial changes of the magnetic properties at the surface region of the TbFeCo layers were detected. These changes were induced by a diffusion of nitrogen from the protective into the magnetic layer leading to a reduced content of magnetically active Tb at the surface. At longer annealing times this led in extreme to a double layer behaviour which makes the medium useless for MO data storage.
  • R. Sbiaa, H. Le Gall, Y. Braïk, O. Koshkina, S. Yurchenko, M. El ...
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_173-176
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      Theoretical investigation of magnetization configurations and reversal processes is presented in exchange-coupled double layer (ECDL) and trilayer (ECTL) with mixed parallel and perpendicular anisotropy structures (F1/F2) and (F2/F1/F2) where F1 is a planar magnetization film corresponding to binary NdCo or ternary GdFeCo amorphous alloy and F2 is a perpendicular magnetization film such as DyFeCo alloy. It is shown from the analytical study that the magnetic profiles are strongly dependent on the magnetic parameters of the layers F1 and F2, the films thickness and the external field along the normal to the film plane which gives the possibility to investigate the magnetization reversal in the multilayers. Calculations are derived in ECDL from a variational method of the magnetic energies in a continuous model and in ECTL from a noncontinuous model. The magnetization profiles and reversal processes are analyzed from an effective exchange induced inside the perpendicular layer F2 by the capping planar layer F1.
  • L. Driouch, R. Krishnan, M. Porte, J. Jonsson, K.V. Rao, M. Tessier
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_177-180
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The magnetic, anisotropy, and the magneto-optic properties of (Co/V)n multilayers prepared by e-beam evaporation under ultrahigh vacuum are presented. The magnetization at 5 K suggests one atomic layer of Co to be nonmagnetic. The overall magnetization is found to have a linear temperature dependence, which indicates a lowered dimensionality in these (Co/V)n multilayers. The surface and bulk anisotropies constant are determined to be at room temperature, Ks = 0.5 erg.cm-2 and Kv = 9.4 106 erg.cm-3, respectively. Polar Kerr rotation (PKR) dependence on t(Co) and t(V) are also presented. It is found that PKR decreases monotonicaly with increasing V thickness for the samples with t(Co) = 22.5 Å.
  • R. Sbiaa, H. Le Gall, O. Koshkina, S. Yurchenko, J. M. Desvignes, Y. B ...
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_181-184
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The temperature dependence of the magnetization processes in mixed exchange-coupled double layers ECDL with a planar GdFeCo film 1 and a perpendicular anisotropy DyFeCo film 2 is analyzed from Faraday rotation measurements. During heating the magnetic state of the ECDL presents strong modifications depending not only on the external field applied along the normal to the layers, but mainly on the ECDL type which can change from a type 1 with an interlayer macroscopic antiferromagnetic (AF) coupling -A12M1.M2 to a type 2 with a ferromagnetic (F) coupling. From appropriate choice of the deposition parameters the films compositions were adjusted for either Tcp1<RT<Tcp2 or RT<Tcp2<Tcp1 where Tcp1,2 are the compensation temperatures of the layer 1 and 2 which gives the possibility to obtain at RT ECDL of type 1/AF or type 2/F respectively. Depending on the respective values of Tcp1 and Tcp2, it is observed by increasing the temperature, F→AF or AF→F type transitions at Tcp1 and Tcp2. The evolutions with the temperature of the magnetooptical (MO) hysteresis loops of the ECDL are explained at the first order from the parallel change of the individual loops of the layers 1 and 2. However very close to Tcp2 more complex MO loops are observed and can be explained from the rise of the hysteresis Hc1 in the planar layer 1 induced by a strong increase of the coercitivity Hc2 of the perpendicular layer 2 near its compensation temperature.
  • Holger Kisker, Takao Suzuki
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_185-188
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The coercivity mechanism in polycrystalline CoCrPt thin films, Co/Pt multilayer systems and in amorphous TbFeCo thin films was studied by analyzing the field and time dependencies of the magnetization. The initial susceptibility X0 and the apparent coercivity as deduced from measuring minor loops indicate a much larger contribution of reversible magnetization processes and a much broader switching field distribution in the polycrystalline CoCrPt magnetic recording medium as compared to the perpendicular magneto-optic Co/Pt and TbFeCo media. The magnetic interactions in the media have been determined by δM measurements yielding the strongest interactions in the amorphous TbFeCo films and the smallest in the polycrystalline CoCrPt films. Analyzing the relaxation behavior of the magnetization the Barkhausen volume was estimated for all the three media and compared with the results from microstructure analysis by TEM and AFM.
  • S. Miethaner, M. Brockmann, F. Himmelhuber, H. Regensburger, F. Bensch ...
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_189-192
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      We have investigated the growth and magnetic properties of ultrathin Fe films on Au(001). The films used for magnetometry have been prepared by MBE on pre-annealed MgO(001) single crystals. Epitaxial growth of the 300-500 monolayer Au buffer layer as well as of the Fe films in the monolayer range could be achieved by use of a Cr seed layer. Epitaxial quality and surface structure was controlled in situ by electron diffraction (LEED, RHEED) and ex situ by STM and AFM. Comparative growth studies were performed for Fe-films on a Au single crystal substrate by in situ STM and ion scattering spectroscopy. We have investigated the magnetic anisotropy of Fe films in the range 3-50 monolayers with alternating gradient magnetometry (AGM). We find a uniaxial out-of-plane contribution of the surface anisotropy which promotes a spontaneous out-of-plane magnetization for films < 2.1 monolayers. Additionally, we report on a fourfold in-plane surface anisotropy, which leads to a switching of the in-plane easy axes into the [110] and [-110] directions for the 3 and 5 monolayer Fe films. We discuss these anisotropy phenomena in context with the breaking of translational symmetry at the interface.
Direct Overwrite and Write Once
  • J.P.W.B. Duchateau, B.A.J. Jacobs
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_193-197
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The phase-change optical disc is one of the most promising candidates for the next generation rewritable, optical discs. For multimedia and video applications, high capacity and high data-rate are required. The choice of the phase-change material, usually a Ge-Sb-Te compound, becomes extremely important since data rate is related to the minimum time for crystallization of the recording material. The availability of high-power, red laser diodes combined with an objective lens with high NA and the application of the mark-edge recording technique, offer the possibility to increase the storage density. We realized a capacity of 2.6 GByte continuous data on a pregrooved disc with a diameter of 12 cm. More than 105 direct overwrite cycles at a bit rate of 18 Mbit/sec were achieved by optimizing the disc structure and recording strategy.
  • D. Raasch, H. Wierenga, H. Borg
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_199-204
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The recording properties of common single layer magneto-optical (MO) disks can be improved by introducing exchange coupled rare-earth (RE) transition-metal (TM) films, both from the point of view of capacity and data transfer rate. MO multilayer stacks must exhibit exchange coupling in order to be suitable for direct overwrite (DOW) and magnetic superresolution (MSR). Thin DOW stacks require an interface layer to adjust the exchange coupling. Soft magnetic Gd-Fe and Gd-FeCo interface layers exhibit suitable magnetic properties to meet the DOW demands. The best solution would be a RE-TM interface layer with inplane anisotropy at room temperature and perpendicular anisotropy at elevated temperatures. Such a layer can also be used as a read-out layer in MSR stacks. Therefore we studied the anisotropy of evaporated and sputtered Gd-TM films as a function of composition. Gd-FeCo films with a Co/(Fe+Co) ratio less than 0.47 showed a transition from inplane to perpendicular anisotropy with increasing temperature. The transition temperature Ttrans depends on the Co/(Fe+Co) ratio and the Gd content and can be adjusted between 0 K and TC. The temperature range ΔTtrans, where the magnetization direction changes from totally inplane to totally perpendicular, was 70 ± 25 K for all evaporated samples while it depends on Ar pressure for sputtered samples. Triple layer DOW disks showed a maximum CNR of 51.4dB.
  • T. Hosokawa, A. Okamuro, K. Miyata, H. Akasaka, A. Sakemoto
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_205-209
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      Among many type of recording media MO storage has higher possibility to progress with improving random access speed and transfer rate, minimizing drive size, and high capacity at the same time. A lot of engineers have thought one of the approach for such improvement is light intensity modulation direct over write method (LIM-DOW). They thought, however, it was hard to mass-produce because LIM-DOW media consists of multiple magnetic multilayer. So we have been using quality engineering (Taguchi method) to improve the efficiency of development. And it was proved that it was possible to do the mass-production of LIM-DOW media.
Domain Physics and Novel Materials
  • Mann Du, Songsheng Xue, Mark H. Kryder
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_211-216
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      We present, for the first time, the direct observation of the dynamic reading process in central aperture detection (CAD) magnetic super resolution (MSR) media. The stroboscopic images taken by a 10ns exposure time high speed Kerr microscope system on an airbearing spin stand are compared with the corresponding CNR measurements on a MO spin stand. Dynamics of the reading process in samples with and without an intermediate layer and at different reading conditions are studied. Our analysis indicates that the intermediate layer sharpens the threshold for copying the data into the readout layer. We find that optimizing the reading power in CAD MSR readout is critical in order to achieve fast copy speed and provide clear and complete copying. The optimal reading power increases with the increase of the linear velocity of the disk, as expected. Higher disk velocity results in a smaller thermal aperture, which is shifted further from the center ofthe optical aperture, resulting in a decrease in CNR.
  • J.P. Jamet, P. Meyer, V. Grolier, J. Ferré, P. Houdy
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_217-221
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      The origin of the thermomagnetic writing of information bits in magnetooptical recording media is not completely solved. The formation of magnetic bubbles during or after the short time local heating of the medium by a focussed laser beam is not yet well understood. Precise time resolved measurements and corresponding calculations are still chalenging. The difficulty of the data analysis comes mainly because thermal and magnetic experimental length scales are of the order of the light wavelength. We present here coupled nanosecond time resolved measurements of the heat diffusion and of the writing process in a Tb/Fe multilayer with a compensation point below room temperature. This enables us to deduce the spatio-temporal variation of the temperature and to prove that the formation of the magnetic bubble occurs during the cooling of our sample. A good fit of our thermal data can only be obtained if the thermal conductivity of our magnetic multilayer is supposed to be more than one order of magnitude smaller than the bulk alloy conductivity.
  • Thomas Schrefl, Josef Fidler
    1996 年 20 巻 S_1_MORIS_96 号 p. S1_223-228
    発行日: 1996年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      Micromagnetic finite element calculations rigorously describe the effects of microstructural features on the magnetic properties of Co/Pt multilayer thin films. Within the framework of static micromagnetism, the hysteresis properties result from subsequent minimum energy solutions for decreasing or increasing applied fields. The concurrent modelling of inhomogeneous magnetic states within the individual grains and of co-operative reversal processes leads to a large-scale optimisation problem. In order to reduce the number of variables, shell elements which account for the multilayer structure and a magnetic vector potential to treat the long-range stray fields are used. Micromagnetic calculations of demagnetisation curves and domain structures in Co/Pt multilayer systems show a qualitative agreement with experimental data obtained from Lorentz electron microscopy. The nucleation field of Co/Pt multilayer increases with improving texture. Spatial fluctuations of the anisotropy directions from grain to grain create barriers for domain wall motion. The pinning field increases with increasing grain size. The coercive squareness improves with decreasing number of bilayers. The ac-demagnetised state shows a maze-like structure. The underlying skeleton shape of the domain structure remains substantially unchanged under an applied field. The transition width and the domain wall jaggedness increase with decreasing quality of texture and increasing grain size.
High Density recording
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