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  • 1
    Electronic Resource
    Electronic Resource
    First principles study of direct exchange coupling between the grains in NiMn antiferromagnets (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7940-7942 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exchange coupling between antiferromagnetic regions of tetragonal NiMn through a separation at a boundary was evaluated by first principles calculation to study the coupling between antiferromagnetic grains. It was assumed that the crystallographic orientation was assumed not to change across the boundary. The layer version of the Korringa–Kohn–Rostoker method was employed to calculate the total energy of the coupled system. The exchange coupling strength was estimated as the total energy difference between the two spin configurations of the two body system, parallel and antiparallel to each other. For the grains without any atomic lattice shift parallel to the plane (100) across the boundary, it was found that the coupling strength decreases more rapidly than that for ferromagnetic hexagonal cobalt with the increase of the separation and that it changes its sign at a separation length of a little greater than a half of the lattice constant. For the case with a boundary across which the lattice shifts by an atomic distance diagonally, the exchange coupling is reduced to about 1/3 of the original value and decreases rather slowly with the increase of the separation compared to the previous case. Those results are consistent with our previous report which predicted the existence of a weak exchange coupling between the grains in an antiferromagnetic polycrystalline layer based on the analysis of a characteristic feature often observed in torque curves for ferro/antiferromagnetic coupled layer systems. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1371945
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  • 2
    Electronic Resource
    Electronic Resource
    Biquadratic coupling effect on magnetoresistance response curves of spin valves with a synthetic antiferromagnet (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6814-6816 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both normal and inverse magnetoresistance (MR) response curves were observed for synthetic spin valves with the structure of Si(100)/Ru/Co(t1)/Ru(0.7 nm)/Co(t2)/Cu(3 nm)/Co(t3)/Ru. Under the assumption of a coherent rotation of the magnetization in the three Co layers, the hysteresis loops, magnetization response, and MR response curves were calculated as a function of the parameters of the system. The parameters include antiferromagnetic coupling of Co(t1) and Co(t2) through Ru layer, a weak ferromagnetic coupling of Co(t2) and Co(t3) through Cu spacer, giant magnetoresistance of the Co/Cu/Co and Co/Ru/Co systems, and AMR contribution of each Co layer. The uniaxial anisotropy of each Co layer and a distribution of the coupling strength of Co(t1)/Ru/Co(t2) were also included. To fit the experimental data well, it was necessary to include a biquadratic coupling in the Co(t1)/Ru/Co(t2) trilayer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360679
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  • 3
    Electronic Resource
    Electronic Resource
    Reconstruction of in-plane magnetization distributions from magnetic force microscope images (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7230-7232 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A three-step method is proposed for reconstructing the in-plane magnetization distribution from a magnetic force microscope (MFM) image. The magnetization distribution is initialized using some assumptions based on our knowledge about domain structures and MFM contrast mechanisms. Then the high-energy moment configurations, which are initialized based on linear variation assumption, are relaxed by performing a micromagnetic calculation using experimentally measured magnetic parameters. A section of a 360° wall in a NiFe/NiO bilayer has been selected to illustrate the reconstruction procedures. It is shown that the method is effective in revealing the wall structure related to the MFM contrast. This method avoids problems caused by noise and nonunique solutions of the micromagnetic equations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355338
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  • 4
    Electronic Resource
    Electronic Resource
    Rotational hysteresis of torque curves in polycrystalline ferro/antiferromagnetic systems (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7546-7548 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rotational hysteresis of ferromagnetic (F)/antiferromagnetic (AF) exchange coupled systems was studied by using NiFe/IrMn, NiFe/FeMn, and NiFe/NiMn samples sputter deposited under almost the same conditions, although the sample of NiFe/NiMn was annealed later to obtain the antiferromagnetic phase for the NiMn layer. The rotational hysteresis of each sample exhibited quite a different feature from each other, especially in the rotational hysteresis–magnetization angle curves. The NiFe/IrMn bilayer showed a dip at around the antiparallel direction to the applied field direction during sample preparation (pinning direction), while the NiFe/NiMn bilayer exhibited a large peak in that direction. The NiFe/FeMn bilayer did not show any noticeable structure in the rotational hysteresis–magnetization curve. Based on the analysis of those data done by using the model recently proposed by the authors, the following was inferred: (1) The distribution of the anisotropy easy axes of IrMn of the NiFe/IrMn bilayer grains is limited in some range of angles around the pinning direction. Some direct exchange coupling exists between the IrMn grains. (2) The distribution of the anisotropy easy axes of FeMn grains of the NiFe/FeMn bilayer is almost random and the direct exchange coupling between the FeMn grains is negligible. (3) In the NiFe/NiMn bilayer, substantial strength of direct exchange coupling exists between some of the grains which switch and the ones which do not switch with the rotation of the magnetization of the NiFe layer, although the volume fraction of the former is much smaller than the latter. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358833
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  • 5
    Electronic Resource
    Electronic Resource
    Training effect of exchange biased iron–oxide/ferromagnet systems (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6910-6912 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Substantial training effect in hysteresis loops was observed in ferromagnet (F)–antiferromagnet (AF) exchange coupled systems of the structure, Si(100)/iron–oxide(tAF)/F layer (5 nm)/Ta(10 nm), prepared by magnetron sputtering. The exchange bias field and the coercivity decrease with increasing number of loop cycles. The initially asymmetric hysteresis loop becomes more symmetric as the number of loop cycles increases. The effect is more prominent in the descending curve starting from the saturation in the positive (parallel to the pinned direction) direction than in the ascending curve of the hysteresis loop. The value of the ascending curve switching field |Hsw+| is rather unchanged while the switching field |Hsw−| in the descending curve decreases drastically with repeated hysteresis loop cycling as was observed in some CoO/Co and NiO/NiFe systems. Those phenomena can be interpreted by a modification of the extended model of Fulcomer and Charap's: the essential modification being the introduction of positive and negative exchange coupling between AF grains. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360682
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  • 6
    Electronic Resource
    Electronic Resource
    Disorder dependence of the magnetic moment of the half-metallic ferromagnet NiMnSb from first principles (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5870-5871 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using half-metallic ferromagnets in spin-dependent devices, like spin valves and ferromagnetic tunnel junctions, is expected to increase the device performance. However, using the half-metallic ferromagnet NiMnSb in such devices led to much less than ideal results. One of the possible sources for this behavior is atomic disorder. First-principles calculations of the influence of atomic disorder on the electronic structure of NiMnSb underline the sensitivity of half-metallic properties in NiMnSb to atomic disorder. In this article, we report on the disorder dependence of the total magnetic moment calculated by applying the layer Korringa–Kohn–Rostoker method in conjunction with the coherent potential approximation. We consider the following types of disorder: (1) intermixing of Ni and Mn, (2) partial occupancy of a normally vacant lattice site by Ni and Mn, and (3) partial occupancy of this site by Mn and Sb. In all cases the composition is kept stoichiometric. All three types of disorder decrease the moment monotonically with increasing disorder levels. For the experimentally seen disorder of 5% Mn and 5% Sb on the normally vacant lattice site, the total moment is decreased by 4.1%. The results suggest that precise measurement of the saturation magnetization of NiMnSb thin films can give information on the disorder. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372550
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  • 7
    Electronic Resource
    Electronic Resource
    Immunoblotting detection of γ-catenin (plakoglobin) antibody in the serum of a patient with paraneoplastic pemphigus (2001)
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 144 (2001), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report a patient with paraneoplastic pemphigus associated with a thymic tumour. Immunoblot study using affinity-purified γ-catenin protein revealed that his serum recognized γ-catenin (plakoglobin) in epidermal, thymic tumour and mouse bladder extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2133.2001.04031.x
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature dependence of exchange field and coercivity in polycrystalline NiO/NiFe film with thin antiferromagnetic layer: Role of antiferromagnet grain size distribution (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4954-4956 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the exchange bias Heb and coercivity Hc, has been measured for a NiO(6.5 nm)/Ni81Fe19(12 nm) bilayer which demonstrated at room temperature zero exchange bias, but an enhanced coercivity (Hc=65 Oe). Upon cooling the sample in a magnetic field (H=300 Oe), the exchange bias remains zero down to T=250 K, whereas the coercivity increases roughly linearly with decreasing temperature. Below this critical temperature an exchange shift of the hysteresis loop occurs that is accompanied by a decrease in the coercivity. Decreasing the temperature further results in an increase in both Heb and Hc. A thermal fluctuation model, where both fluctuating and stable AF grains contribute to the coercivity, with an additional assumption of increasing the density of NiO interfacial uncompensated spins at low temperature, predicts the correct temperature behavior of Heb and Hc. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373213
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  • 9
    Electronic Resource
    Electronic Resource
    Study of 360° domain walls in NiFe/NiO film by tip–sample interaction on magnetic force microscope (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6484-6486 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The 360° domain wall loops were studied using a magnetic force microscope (MFM) in a glass/Ta(10 nm)/NiFe(12 nm)/NiO(6 nm)/Ta(5 nm) multilayered film fabricated by magnetron sputtering. The film had an enhanced coercivity but no M–H loop shift due to the thin NiO layer. It was found that the local magnetic field exerted by a MFM tip can strongly affect the 360° domain wall, and this interaction was used to probe the structure and dynamics of the wall. The repeated scanning action of the tip causes the transformation from a 360° wall loop into a 180° wall loop. The magnetization distributions for these domain walls were derived from the MFM images. The mechanism of the irreversible change of wall structures caused by the tip–sample interaction was investigated based on micromagnetic analysis. The study of the transformation process provided a better understanding of the structures of the 360° walls. This work suggests that the tip–sample interaction could be a useful tool for studying the domain wall structures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372745
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  • 10
    Electronic Resource
    Electronic Resource
    Status of the HIMAC pulsed Penning source : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 972-974 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Since 1994 at the National Institute of Radiological Sciences HIMAC, the NIRS Penning ionized-gauge ion source (PIGIS) has so far been used for radiotherapy with carbon beams and for basic research with several ion species. The source can produce beams from H2 to Fe with a charge-to-mass ratio of between 1/7 and 1/2. It is a hot-cathode type with a filament, of which the lifetime is on the order of a week and the cathode on the order of 1 month, under a low-duty pulsed operation (≤0.5%) synchronized to the ring operation. This PIGIS can produce highly charged ions: for example, 1 e mA of Ar7+ or 500 eμ A of Si5+ ions (by sputtering) under the typical arc power of 5 kW in peak. This article describes the present status of the NIRS-PIGIS. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150362
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