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  • 1
    Electronic Resource
    Electronic Resource
    Effect on magnetoresistance and magnetic properties of Co/Cu/Co/CoO films with a thin Co layer inserted within the Cu layer (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4734-4737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We find that sandwich films of the form Co50 A(ring)/Cu (t)/Co50 A(ring) with a CoO overlayer have large negative magnetoresistance [(MR)—up to 15% at T=4.2 K] for Cu thickness t(approximately-greater-than)10 A(ring). The MR correlates with a plateau in the magnetization curve which indicates antiparallel magnetization directions of the Co layers as caused by exchange coupling from the antiferromagnetic CoO overlayer. The addition of Co layers 2 or 4 A(ring) thick inserted midway in the Cu spacer can increase or decrease the MR depending on Cu spacer thickness. When comparing sandwich films with and without the insert layer, MR agrees in magnitude if 1/2 the total Cu thickness is used for the insert film. This means that it is only necessary to have a 2 or 4 A(ring) Co layer to scatter spin polarized electrons and implies that interface scattering at a boundary between Co and Cu may dominate over bulk scattering. For films with or without Co insert layers, a metallic Cu overlayer of 20 A(ring) thickness, causes the magnetization plateau to disappear and reduces the MR to less than 1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357241
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetoresistance and magnetic properties of NiFe/oxide/Co junctions prepared by magnetron sputtering : The 6th joint magnetism and magnetic materials (MMM)−intermag conferenc (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6104-6106 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NiFe/oxide/Co junctions were fabricated by magnetron sputtering for studies of polarized electron transport across the insulating barrier. Al2O3, Al-Al2O3, and MgO insulating barriers were prepared with junction resistances from 0.5 to 116 Ω. The I-V characteristics at room temperature are linear. For low barrier resistance, the magnetoresistance of the structure is dominated by the anisotropic magnetoresistance of the ferromagnetic electrodes. For the higher barrier resistances, a different magnetoresistance effect is observed, which is tentatively related to tunneling or spin-valve effects across the insulating junction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358319
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  • 3
    Electronic Resource
    Electronic Resource
    Spin-valve structures exchange biased with a-Tb0.23Co0.77 layers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6480-6482 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin-valve structures, glass/NiFeI/Cu/NiFeII/a-TbCo/Cu, were prepared where the pinned Permalloy layer is exchanged biased by a 200 to 400 A(ring) thick a-Tb0.23Co0.77 layer. Exchange fields between 50 and 250 Oe were achieved with TbCo thicknesses below 400 A(ring), for a pinned Permalloy layer 150 A(ring) thick. The exchange fields are strongly dependent on substrate bias. The magnetoresistance of these structures reaches 4.5% when thin Co layers are added at the NiFe/Cu interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356970
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetoresistance and exchange effects of NiCo/Cu sandwich films with oxide overlayer : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6537-6539 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR) of 8% at 4.2 K is found in sandwich films having the composition Ni0.7Co0.3(50 A(ring))/Cu(t)/NiCo(50 A(ring))/NiCoO(40 A(ring)) where NiCoO is a mixed oxide overlayer that exchange couples with the NiCo alloy layer. These films show a MR temperature dependence quite similar to that previously reported for Co/Cu/Co/CoO where the MR becomes small above 200 K. When bilayers of CoO/NiO are placed on the NiCo layer, the temperature dependence of MR extends to 250 K. The magnitude of the MR at 4.2 K scales with the magnitude of the saturation magnetization in the NiCo and Co films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356940
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  • 5
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance in Co/Cu multilayers after annealing : 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. 6601-6603 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayer films of [Co 10 A(ring)/Cu(t)]64 with copper thicknesses from t=10 to 29 A(ring) annealed for 1 h at temperatures about 350 °C showed a decrease in sample resistivity at 4.2 K. The giant magnetoresistance (GMR) maximums for as-deposited films at t=10 A(ring) and t=23 A(ring) shifted with annealing. The GMR decreased for t=10 A(ring) and t=23 A(ring) but increased for t=19 A(ring) and t=29 A(ring) indicating a complex behavior with annealing. Similarities with granular films are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358206
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  • 6
    Electronic Resource
    Electronic Resource
    Transport properties in amorphous Ux-T1−x films (T=Fe, Ni, Gd, Tb, and Yb) (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5453-5458 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe the competing magnetic, localization, and phonon effects on the transport properties of amorphous magnetic UxT1−x films, with T=Fe, Ni, Gd, Tb, and Yb. Amorphous UxFe1−x films change from collinear to random ferromagnetism as x increases, and the temperature dependence of the resistivity denotes the competing effects of spin-flip and non-spin-flip exchange scattering processes. The resistivity has a minimum at Tf rising sharply below this temperature. The sign of the magnetic resistivity and the magnetoresistance indicates 〈Si ⋅Sj 〉〉0, while the anisotropic magnetoresistance indicates a local exchange gap. Amorphous UxGd1−x and a-UxTb1−x are, respectively, spin glasses and random anisotropy dominated systems. The resistivity increases smoothly through Tf and has a slight upturn at low temperatures that we associate with weak localization. The magnetoresistance is negative in both systems and the anisotropic magnetoresistance is null, although the applied field induces anisotropic behavior in the Tb containing films (asperomagnets). All samples show quadratic and positive field dependence of magnetoresistance well inside the paramagnetic regime, and a linear regime below Tf. At low temperatures and in the a-UxGd1−x films, negative (H)1/2 and H2 regimes occur and are associated with weak localization processes dominated by the inelastic mean free path.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342346
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  • 7
    Electronic Resource
    Electronic Resource
    Random-anisotropy ferromagnetism in amorphous U27Fe73 films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3746-3748 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measured magnetic and transport properties of amorphous U27Fe73 films deposited by magnetron sputtering. The films show a magnetic ordering temperature Tf =32 K, and a spin-glass regime below a temperature Tirr(H). The Arrott plot shows a characteristic change in concavity at the transition, as predicted by Aharony and Pytte (A-P) for random-anisotropy systems with D(very-much-less-than)J. Although we find a finite susceptibility below Tf, with χ0=0.66 in units of the inverse of the demagnetizing factor, the critical exponents δ1 and δ2 are close to the values predicted by the A-P model. The electrical resistivity has a minimum at 31 K, resulting from the competition between exchange scattering and inelastic spin-flip processes. For T〉200 K a linear regime with negative dρ/dT is found, characteristic of phonon scattering in amorphous materials. The isotropic magnetoresistance is positive and levels off below Tf reflecting freezing of spin correlations at this temperature. This behavior can be explained by the existence of small Imry and Ma domains and partial local magnetic order below Tf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340654
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  • 8
    Electronic Resource
    Electronic Resource
    TbxNdy(FeCo)1−x−y: Promising materials for magneto-optical storage? (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3349-3351 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the pseudoternary system TbxNdy(FeCo)1−x−y is presented focusing on key parameters for magneto-optical storage applications. For compositions with perpendicular anisotropy at room temperature (x〉0.08; 0.4〉z+y〉0.15) the Kerr rotation (λ=633 nm) increases with FeCo concentration for a given x/y ratio and increases also with the Nd concentration for a given FeCo concentration. The latter effect is more pronounced at λ=420 nm than at λ=800 nm. Room-temperature compensation is found at x=0.2 for all of these compounds indicating a Nd moment parallel and, in magnitude, similar to the FeCo moment. The high-temperature magneto-optical measurements revealed a significant lowering of the anisotropy constant at elevated temperatures with Nd concentration, which leads to a loss of square loops already 100 K below TC for certain compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338766
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetoresistance and magnetic properties of Co/Cu/Co sandwich film with thin Co layer insert (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5541-5541 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The enhanced magnetoresistance (MR), also called "spin valve,'' found by Speriosu et al.1 in sandwich layers of the form Co(50 A(ring))/Cu(t)/Co(50) has been modified by addition of Co 2 and 4 A(ring) insert layers midway in the Cu(t) layer of thickness t. The insert was suggested by Slonczewski2 as a method to influence the exchange coupling between the Co layers. In addition, we have also studied the effect of Cu overlayers on the MR and magnetic properties. The films are prepared by computer controlled magnetron sputtering from Co and Cu targets with Cu(t) varied from 20 to 36 A(ring). For MR values above 1% there is a pronounced plateau and hysteresis in the magnetization (M) versus applied field (H) curve and a corresponding plateau and hysteresis in MR versus H. The effect of the Co insert layers on MR is dependent on the Co insert thickness and also the Cu thickness. For example, for Co(x) in Co(50 A(ring))/Cu(18)/Co(x)/Cu(18)/Co(50) there is an increase in MR of 11%–14% for x=0–4 A(ring). In contrast, Co(50 A(ring))/Cu(14)/Co(x)/Cu(14)/Co(50) showed a decrease of 14%–6% for x=0–4 A(ring). Measurement of the MR temperature dependence for Co(50 A(ring))/Cu(28)/Co(50) showed a Brillouin-like decrease going from 14% at 4.2 K to less than 1% at 185 K. Another method to cause large changes in MR for the sandwich structures, either with or without the Co insert layer, is the addition of an overlayer of Cu of 10 or 20 A(ring). For the 10 A(ring) overlay, there is up to a 50% decrease in the extent of the plateau as well as MR; for the 20 A(ring) Cu both the plateau and MR have been reduced to almost zero. At this time, we cannot fully interpret the Cu overlay mechanism but its understanding should lead to improved control over the properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353643
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetoresistance in (Co10 A(ring)/Cu10 A(ring))n multilayer films as n increases : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6378-6380 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayers of Cu10 A(ring)/(Co10 A(ring)/Cu10 A(ring))n, where n is the number of bilayers, shows a nonlinear increase of magnetoresistance ratio (MR%) with increasing n. For each value of n the resistivity decreases with applied field. MR values at 4.2 K are less than 2% for n≤16 but increase to 38% at n=128. Conduction electron mean free paths (l), calculated from film resistivity as a function of total film thickness, increase from l=150 to 470 A(ring) when the applied magnetic field changes from zero to 18 kOe. The values obtained for l indicate that for n≤16 MR is reduced by diffuse surface scattering while for n≥16 MR surface scattering is less important and the Co atomic moment ordering is the most important factor. About half the decrease in resistivity with field is associated with the final 2% increase in magnetization for fields above 5 kOe which we interpret in terms of Co interface disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352656
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