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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic and structural properties of CoCrTaNiPt longitudinal thin-film media (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6866-6868 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Ni addition on magnetic and structural properties of CoCrTaNiPt/Cr longitudinal media fabricated under the UC process have been investigated. It is found that the addition of Ni up to 13 at. % increases the magnetocrystalline anisotropy field of grain Hkgrain by 10%, and decreases the saturation magnetization Ms by 20%. As a result, coercivity Hc increases by 10%–15% and the ratio of the saturation flux density to anisotropy field 4πMs/Hkgrain decreases by 30%. Further addition of Ni from 13 to 19 at. % results in a decrease of Hc by 7% and a decrease of Hc/Hkgrain from 0.38 to 0.36. This is due to the degraded grain-boundary structure and the increase of the stacking fault density. The addition of Ni up to 13 at. % is effective in increasing Hkgrain and decreasing 4πMs/Hkgrain, while retaining a high Hc/Hkgrain value of about 0.38. As a result, Hc as high as 3.2 kOe is obtained even when using an isotropic NiP/Al substrate. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372868
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  • 2
    Electronic Resource
    Electronic Resource
    Enhanced exchange anisotropy of Ni–Fe/Mn–Ni bilayers fabricated under the extremely clean sputtering process (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4919-4921 
    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 exchange anisotropy of ferromagnet/antiferromagnet bilayers, Ni–Fe/Mn–Ni films were prepared under different purities of the sputtering atmosphere by changing the base pressure from 10−11 Torr [extremely clean (XC) process] to 10−7 Torr [lower grade (LG) process]. The correlation between the exchange anisotropy and the microstructure of the films is discussed. As a result, we found that: (1) The exchange anisotropy was enhanced in the XC processed films comparing to the LG processed ones, especially when the thicknesses of both the ferromagnetic and antiferromagnetic layers were very thin. (2) The critical thicknesses of the antiferromagnetic layers were 110 and 150 Å for the XC and the LG processed films, respectively. (3) In the XC processed films, the fcc-[111] direction of the Ni–Fe grains were highly oriented perpendicularly to the film plane and an enlargement of antiferromagnetic grains was observed. We conclude that the enhancement of exchange anisotropy is caused by the enlargement of antiferromagnetic grains in the XC processed films. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369142
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Effect of an Fe–Si buffer layer on the magnetoresistance of a Co/Cu multilayer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4461-4467 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Cu multilayers were fabricated on a thermally oxidized Si wafer (SiO2 substrate) as well as a bare Si wafer (Si substrate). The multilayer had an Fe buffer layer and was produced in a sputtering atmosphere into which oxygen was introduced. In the case of the Si substrate, the magnetoresistance (MR) ratio increased as the partial oxygen pressure decreased below 3×10−8 Torr, whereas it steeply decreased in the case of the SiO2 substrate. The increase in the MR ratio in the case of the Si substrate was due to an enlargement of the lateral grain size of the multilayers, which reduced the interfacial roughness of the multilayer. When Fe–Si was used as the buffer layer, the MR ratio of the multilayer on the SiO2 substrate drastically changed in relation to the buffer layer's Si content. A maximum MR ratio of 40% was obtained at 16% Si, corresponding to the enlargement in the lateral grain size. The MR ratio of the multilayer fabricated on the Fe82Si18 buffer layer remained 28% after annealing at 350 °C. We therefore conclude that the Fe–Si buffer layer is effective in facilitating the lateral grain growth of Co/Cu multilayers and in attaining high thermal stability of the MR ratio. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1459105
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  • 5
    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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  • 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
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic moment of α″-Fe16N2 films (invited) : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6642-6647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine the value of the intrinsic magnetic moment of the α ‘ phase, the films of nitrogen-martensite with various N content were fabricated under various reactive sputtering conditions. The magnetic moment of (α ‘+α')-Fe16N2 films is discussed in connection with the change of the unit-cell volume of the bct structure and the degree of N site ordering in nitrogen-martensite. As a result, it is found that (1) the same structure as bulk α ‘-Fe16N2 is realized in the present films, (2) the saturation magnetization σs of the α' phase increases about 4% with increasing unit-cell volume of the α' phase, (3) the degree of N site ordering from α' to α ‘-Fe16N2 does not much affect σs, and (4) the experimentally obtained maximum value of σs for the (α ‘+α')-Fe16N2 film was 232 emu/g. The intrinsic value of σs in the α ‘ phase (in the perfectly ordered state) is proposed to be no more than 240 emu/g at 300 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358431
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  • 10
    Electronic Resource
    Electronic Resource
    Dependence of media noise on grain size and intergranular coupling in thin-film media : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5339-5341 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The media noise performance is discussed in connection with grain size and intergranular coupling for the Co85.5Cr10.5Ta4, Co78Cr17Ta5, and Co62.5Ni30Cr7.5 thin-film media fabricated under the ultraclean sputtering process (UC process). It is clarified that the value of S/Nm is quantitatively represented as functions of the value of Hc/Hkgrain and the grain size in every kind of media. The value of signal-to-media noise ratio (S/Nm) increases with the increment in Hc/Hkgrain and also with the decrement in grain size. In the media with grains adequately separated by segregated grain boundaries fabricated by the UC process, grain-size reduction, taking account of the decrease in intergranular magnetostatic coupling, is required to obtain even higher S/Nm values. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361371
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