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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of metal hydroxide-layer silicate intercalation compounds (metal = Mg(II), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), Zn(II), and Cd(II)) (1990)
    s.l. : American Chemical Society
    Chemistry of materials 2 (1990), S. 511-517 
    Details
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cm00011a009
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure and giant magnetoresistance of Co–Cu granular films fabricated under the extremely clean sputtering process : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7004-7006 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to clarify the influence of the impurities in the sputtering atmosphere on the microstructure and the giant magnetoresistance (GMR) properties of nanogranular thin films, Co–Cu alloy films were prepared on quartz substrates at room temperature under the different purity of the sputtering atmosphere by changing the base pressure, 10−11 Torr extremely clean process (XC) and 10−7 Torr lower grade process (LG). The correlation between the microstructure and the GMR of films after an annealing procedure is discussed. As results, we found that; (1) A Co-rich phase combined with oxygen was formed at grain boundary in the films as deposited under the LG process; (2) the gradual progress of the grain growth of precipitates with increasing annealing temperature was observed in the XC-processed films, while the coarse grain growth of the matrix phase, resulting in the abrupt change of magnetoresistance occurred in the LG-processed films. We conclude that regulated impurity concentration in the films is an essential parameter to control the precipitation process from the supersaturated solid solution and to realize the desirable microstructure of the nanogranular GMR thin films. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367625
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  • 3
    Electronic Resource
    Electronic Resource
    Role of oxygen in the film growth and giant magnetoresistance of Co/Cu multilayers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6308-6313 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to clarify the effect of oxygen in the sputtering atmosphere on the microstructure and giant magnetoresistance, Co/Cu multilayers were fabricated under a sputtering atmosphere into which regulated impurity oxygen gas was introduced. After being pumped down the sputtering chamber to the ultimate pressure (less than 1×10−10 Torr), oxygen was introduced into the chamber until its content in processing Ar gas was about 0.1 ppm to 0.1%. The magnetoresistance (MR) ratio drastically increased from less than 20% to 54% when the content of impurity oxygen was slightly increased from 20 to 80 ppm, then nearly vanished when the content became more than 200 ppm. In the former region where the MR ratio steeply increased, the root mean square roughness of the multilayers decreased from 6.5 to 4.5 Å accompanied by a reduction in grain size as the oxygen content was increased. The partial oxidation of the multilayers is the most probable mechanism by which the flattening of the interfaces in the multilayer can be explained. We conclude that the impurity oxygen in the sputtering atmosphere serves as an obstruction of grain growth in the multilayer, not as a surfactant for the film growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1367877
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  • 4
    Electronic Resource
    Electronic Resource
    Enhancement of exchange bias in Mn–Ir/Co–Fe based spin valves with an ultrathin Cu underlayer and in situ Mn–Ir surface modification (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6609-6611 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Enhancement of exchange bias induced at the interface of the antiferromagnetic (AF)/ferromagnetic (F) layers was studied using the bottom "spin-valve films" (SVs) with the Mn–Ir/Co–Fe exchange coupled films. Exchange bias increased using an ultrathin Cu underlayer. Meanwhile, both exchange bias field, Hex, and blocking temperature, TB, increased intensively by heating specimens after depositing Mn–Ir film in a high vacuum. These two enhancement effects worked in an additive. As a result, an unidirectional anisotropy constant, JK, of 0.39 erg/cm2 (Hex of 1.3 kOe) and TB of ∼325 °C were obtained for the bottom SVs with a total thickness of 233 Å including an AF layer of 68 Å Mn74Ir26 and a pinned layer of 20 Å Co90Fe10, where the SVs were field annealed at 320 °C. A microstructural analysis using x-ray diffraction revealed that Hex did not depend on the diffraction intensity from Mn–Ir (111) for the SVs with various underlayers, and no remarkable changes occurred in the microstructure of the SVs with the heating treatment in a vacuum. Therefore, the enhancement effects might result from some changes in the microstructure and/or the morphology of the interface of AF/F layers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357146
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  • 5
    Electronic Resource
    Electronic Resource
    Single spin ensemble model for the change of unidirectional anisotropy constant by annealing on polycrystalline ferromagnetic/ antiferromagnetic bilayers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4957-4959 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model for the exchange coupled polycrystalline ferromagnetic/antiferromagnetic (F/AF) bilayers is proposed in order to discuss the mechanism of the change of the unidirectional anisotropy constant (JK) of the bilayers by thermal annealing. The AF layer is treated as an aggregation of the AF grains whose magnetic anisotropy axes lay in the film plane with two-dimensionally random distribution. Two stable states concerning the direction of the AF spins are calculated for the AF grain. Determining the populations of the AF grains in each state in thermal equilibrium, total energy of the system is obtained, which provides the magnetization curves and the magnetic torque curves of the F/AF bilayers. The calculated results show the reduction of JK with increasing the equilibrium temperature, which is due to the changes of the probability functions for the respective spin alignments of the AF grain. We conclude that the changes in JK do not necessarily need any changes of the microstructure and the intrinsic physical quantities of the F/AF bilayers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373214
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy in antiferromagnetic layers affecting exchange bias of Ni–Fe/Mn–Ir bilayers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4930-4932 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic anisotropy of antiferromagnetic layers (KAF) was estimated for Ni–Fe 50 Å/Mn–Ir dAF bilayers using Mauri's method (dAFcr=JKs/KAF), where JKs is the saturation value of the unidirectional anisotropy constant (JK). The critical thickness of the antiferromagnetic layers (dAFcr), at which JK took half the value of JKs, was determined from the dependence of JK on dAF. The dAFcr was found to be almost constant (35±2 Å) independent of JKs. Thus, the relation of JKs∝KAF was derived, suggesting that the variation in JKs is due to a change in the value of KAF. JKs, however, was found to vary considerably for various Mn–Ir films possessing an almost identical Ir content, and thus probably the same value of KAF. In addition, studies by x-ray diffraction, transmission electron microscopy, and electron diffraction revealed that the change in JKs was independent of the microstructure and phase of the antiferromagnetic (AF) Mn–Ir films, both of which control KAF. Thus, JKs was found to be independent of KAF contradicting the relation, JKs∝KAF. This contradiction results from the assumption by Mauri that the coupling energy (J) is equal to JKs even in the polycrystalline exchange-coupled bilayers. A model that took account of the distribution of KAF axes of AF grains in the plane of the AF film successfully explained the behavior of JK. JKs was found to change independent of both J and KAF, and furthermore, it has been shown that the dependence of JKs on the sputtering conditions for Mn–Ir films is probably due to the effective temperature of the films during deposition. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373206
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  • 7
    Electronic Resource
    Electronic Resource
    Drastic change of giant magnetoresistance of Co/Cu multilayer by decreasing residual impurities in sputtering atmosphere (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4463-4465 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to clarify the influence of residual impurities in the sputtering atmosphere on the microstructure and the giant magnetoresistance (GMR), Co/Cu multilayers were fabricated by changing the chamber pressures, Pb, just before introducing processing gas. Pb was controlled by changing the pumping time after venting the chamber with air. A drastic change of magneto resistance (MR) ratio from 48% to 14% was observed, when Pb was changed slightly from 7×10−8 to 3×10−8 Torr. In that Pb region, the root mean square (rms) roughness increased discontinuously from 3.7 to 4.6 Å as Pb was lowered. The abrupt drop of the MR ratio was accounted for by the decrease of the antiferromagnetic coupling accompanied by the increase of interfacial roughness. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370375
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  • 8
    Electronic Resource
    Electronic Resource
    Orientational dependence of the exchange biasing in Ni–Fe/Mn1−xNix (x=0.11, 0.18, 0.23) bilayers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4925-4927 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The correlation between the exchange anisotropy of ferromagnetic (F)/antiferromagnetic (AF) bilayers and the spin alignment of antiferromagnet at the interface is still under question. In the present study, Mn1−xNix (x=0.11,0.18,0.23) alloys, whose spin structure changes with x, were used for Ni–Fe/AF bilayers. The correlation between AF spin alignment at the interface and exchange anisotropy was investigated by controlling the preferred orientation of the bilayers. The crystal orientation of bilayers was changed by adding nitrogen into the sputtering argon gas only during the deposition of the Ni–Fe layer adjacent to the substrate. The preferred orientation was (111) when the nitrogen partial pressure, PN2=0%–1%; (100) when PN2〉1%. When PN2〈1%, Jk decreased and Hc increased with increasing PN2, because of the decrease of the grain size of γ-Mn–Ni. When PN2 exceeds 1%, Jk increased discontinuously, accompanied by the orientational change of the bilayers. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369144
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy and rotational hysteresis loss in exchange coupled Ni–Fe/Mn–Ir films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4375-4388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic anisotropy and rotational hysteresis loss in Ni–Fe/Mn–Ir bilayers were investigated for films prepared by an ultraclean sputtering deposition process. An in-plane field of 30 Oe during deposition served to define the antiferromagnetic (AF) alignment axis for the Mn–Ir layer. The Ni–Fe layer thickness was maintained at 50 Å and the Mn–Ir layer thickness ranged from 20 to 200 Å. Room temperature magnetization and torque measurements were made as a function of the Mn–Ir layer thickness dAF and the applied field. The magnetization data were obtained for fields applied in the same direction as during deposition. The magnetization data indicate a critical dAF value of 37 Å, taken as dAFcr. For dAF〉dAFcr, the data show hysteresis loops which are displaced along the field axis. The torque response and rotational hysteresis characteristics are sensitive to both dAF and the measuring field. (1) When dAF is much less than dAFcr, the torque curves have a sin θ characteristic at fields below 30–40 Oe or so which suddenly changes to a sin 2θ characteristic at higher fields. With the onset of the sin 2θ torque response, rotational hysteresis loss also appears but then vanishes for fields above 100 Oe or so. (2) As dAF approaches dAFcr from below, the torque response is the same as above. Here, however, the rotational hysteresis appears for fields well below the field at which the torque response assumes a sin 2θ character and persists to the maximum available measuring field of 15 kOe or so. (3) When dAF exceeds dAFcr, the torque has a predominant sin θ character at all fields and a small sin 2θ component and rotational hysteresis which only around a field of 400 Oe or so. These results, while somewhat complicated, are in accord with responses evaluated from the simple exchange anisotropy model of W. H. Meiklejohn and C. P. Bean [Phys. Rev. 102, 1413 (1956); 105, 904 (1957)]. Among other things, one may conclude that a rotational hysteresis which persists to high field is not intrinsic to exchange anisotropy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373081
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  • 10
    Electronic Resource
    Electronic Resource
    Field independent rotational hysteresis loss on exchange coupled polycrystalline Ni–Fe/Mn–Ir bilayers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6415-6417 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behaviors of the magnetic torque curve and the rotational hysteresis loss of the polycrystalline ferromagnetic (F)/antiferromagnetic (AF) bilayer whose AF layer is thinner than the critical thickness are discussed as a function of the applied field. The critical thickness of the AF layer is the threshold beyond which the unidirectional anisotropy appears. At the high field, we found some differences between the calculated torque curves based on the simple model proposed by Meiklejohn and the measured ones for the Ni–Fe/Mn–Ir bilayer: (1) the lack of the sin 2θ component and (2) the constant rotational hysteresis loss, in the experimental results. These differences are explained well by the model in which the two-dimensionally random distribution of the magnetic anisotropy axes of the AF grains is taken into account. We conclude the distribution of the anisotropy axes of the AF grains is an indispensable factor to understand the unidirectional anisotropy of the polycrystalline F/AF bilayers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372723
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