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  • 1
    Electronic Resource
    Electronic Resource
    Structure, magnetic properties, and giant magnetoresistance in melt-spun metallic copper–cobalt ribbons (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1979-1990 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a comprehensive investigation of structural, magnetic, and transport properties of as-quenched and annealed CoxCu1−x (0≤x≤0.20) granular alloys prepared by melt spinning. Using x-ray diffraction, differential scanning calorimetry measurements, and magnetic characterization, we have uncovered a Co phase separation process which results in the variation of magnetic and transport properties of Co–Cu heterogeneous alloys. In the Co composition range (0≤x≤0.15), the maximum giant magnetoresistance (GMR) was observed for CoCu samples annealed at 450 °C for 30 min, where Co particle diameters are in the range of 3.5–4.5 nm. The variation of magnetic and transport properties with the concentration and size of precipitated Co clusters is discussed, and is consistent with the prediction of the two-channel model, in which spin-dependent scattering is dominated by the cluster-matrix interfaces. The reduction of GMR in high Co concentration is attributed to the appearance of magnetic coupling among magnetic particles. In contrast, very small particles tend to behave superparamagnetically, resulting in the reduction of the ratio of spin-dependent scattering to spin-independent scattering potentials, and thus in the reduction of the GMR effect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361049
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties and giant magnetoresistance of magnetic granular Co10Cu90 alloys obtained by direct-current joule heating (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5062-5066 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The direct-current (dc) joule heating technique was exploited to fabricate giant magnetoresistance (GMR) Co10Cu90 granular alloys. The Co cluster precipitation process was investigated by calorimetric and x-ray diffraction measurements. At T=10 K, the largest MR change of 25.0% has been observed for the melt-spun Co10Cu90 ribbon annealed at I=5 A. The magnetoresistance scales approximately as the inverse Co particle size. At room temperature, it was found that the dc joule-heated samples show relatively high GMR in comparison with furnace-annealed samples. Based on the phenomenological GMR model, we assumed that it is a consequence of smaller Co particles formed in dc joule-heated samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359735
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic properties and giant magnetoresistance in melt-spun Co-Cu alloys (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 392-397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic, structural, and transport properties of as-quenched and annealed Co10Cu90 samples have been investigated using x-ray diffraction and a SQUID magnetometer. The largest value of MR change was observed for the as-quenched sample annealed at 450 °C for 30 min. The magnetic and transport properties closely correlate with the microstructure, mainly with Co magnetic particle size and its distribution. For thermal annealing the as-quenched samples below 600 °C, the Co particle diameters increase from 4.0 to 6.0 nm with a magnetoresistance (MR) drop from 33.0% to 5.0% at 10 K. Comparison with the theory indicates that the interfacial electron spin-dependent scattering mechanism correlates with GMR for Co particle diameters up to about 6.0 nm. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360613
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  • 4
    Electronic Resource
    Electronic Resource
    Magneto-impedance effect in soft magnetic tubes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4807-4809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft magnetic crystalline alloys have been fabricated in a tube form by electrodepositing magnetic FeNi and FeNi–Al2O3 onto W fibers with a diameter of 25 μm. Fine Al2O3 particles have also been incorporated into the magnetic matrix to improve mechanical properties. As-prepared materials are not magnetically soft. With heat treatment, the magnetic properties of these composites are similar to commercial bulk soft FeNi alloys. A giant magnetoimpedance value as large as 190% has been found in as-prepared FeNi-W with a magnetic layer thickness of 20 μm. This value is comparable to GMI observed in amorphous magnetic wires. Experiments also show that GMI values decrease when the Al2O3 content increases in a range from 0 to 7.0 at. %. This behavior is due to the increase in electrical resistivity and magnetic permeability of the samples that modifies the skin effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373166
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  • 5
    Electronic Resource
    Electronic Resource
    Memory effect in standard spin valve structures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4951-4953 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Memory effect has been observed in both standard top and bottom spin valves. The change of the magnetization state in the pinned FM layer, below the blocking temperature, reverses the direction of the exchange bias and destroys the magnetoresistance properties. This reversed exchange bias is much weaker, causing severe consequences in SV applications. This behavior can be explained in terms of blocking temperature distribution in the AFM layer perhaps due to the structural randomness. By varying cooling procedures, the exchange coupling in regions with different blocking temperatures can be separated. It is found that the maximum exchange bias is very close to the sum of the exchange biases in different regions. The domain wall energy in the FM layer has to be taken into account in order to explain the behavior of the reversed bias. The insertion of a synthetic antiferromagnetic subsystem (Co/Ru/Co) stabilizes the magnetization state in the pinned layer because of the additional interlayer coupling through the Ru layer. This suppresses the memory effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373212
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  • 6
    Electronic Resource
    Electronic Resource
    Novel soft magnetic composites fabricated by electrodeposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5840-5842 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft magnetic composites have been fabricated by electrodepositing FeNi and FeCo onto W fibers with a diameter of 20 and 100 μm. Structural and compositional characterizations indicate that FeNi and FeCo-based composites are of fcc and bcc structure, respectively. The mechanical strengths are significantly improved depending on the volume fraction of W fibers. To further improve the mechanical properties of these composites, we have codeposited soft magnets and Al2O3 powders, resulting in an increase in Vickers hardness of more than 100%. Magnetic measurements show that as-deposited fibers are not magnetically soft. After proper thermal annealing, the samples exhibit excellent soft magnetic properties. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372540
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  • 7
    Electronic Resource
    Electronic Resource
    Pinning effect of the grain boundaries on magnetic domain wall in FeCo-based magnetic alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6655-6659 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the dynamics of grain growth and the pinning effect of grain boundaries on magnetic domain walls in FeCo soft magnetic alloys. It has been found that grain growth takes place at temperatures above 600 °C. The activation energy for grain growth in a disordered state at 820 °C is about 57.4±0.5 kcal/mole. The effect of grain size on magnetic properties has been singled out by keeping the same ordering parameter (S=0 and 0.88) for all samples studied. Microstructural characterization and magnetic measurements indicate that the grain size significantly affects the magnetic coercivity. A linear relationship between the coercivity and the reciprocal of the grain size has been universally found regardless of the heat-treatment histories. Lorenz microscopic observation demonstrates that grain boundaries act as pinning sites for the magnetic domain wall movement. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370175
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  • 8
    Electronic Resource
    Electronic Resource
    Memory effect and temperature behavior in spin valves with and without antiferromagnetic subsystems (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5692-5695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature behavior and memory effect in standard spin valves (SV) and SVs with synthetic antiferromagnetic (Co/Ru/Co) (SV-SAF) subsystems have been studied. SV-SAFs show much better temperature stability. Memory effect refers to the phenomenon that the exchange bias can be altered at temperatures (TR's) much lower than the blocking temperature (TB), and these temperatures (TR's) are imprinted into SVs. The memory effect greatly deteriorates the magnetoresistance behaviors in SV. Our results suggest that the memory effect is caused by a distribution of local blocking temperatures (Tb's). The magnetization state in the pinned layer is critical in determining the temperature behavior of HE and magnetoresistance. By partially reversing the magnetization in the pinned ferromagnetic (FM) layers, we are able to separate the temperature dependencies of the local exchange bias (He) associated with regions consisting of different Tb's. Two features have been observed: (1) the local exchange bias (He) with a narrow Tb distribution has a weak temperature dependence; (2) the simple algebraic sum of local He's nearly reproduce the total HE with the difference between these two quantities representing the domain wall energy in the FM layer. On the other hand, SV-SAFs show strong resistance to memory effects because of two factors; the strong exchange coupling through the Ru layer, and the net magnetic moment of Co/Ru/Co layers in SV-SAF being close to zero. The former makes the two SV-SAF FM layers behave coherently, while the latter makes the interaction between the SV-SAF and the external field negligibly small. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371580
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  • 9
    Electronic Resource
    Electronic Resource
    Temperature dependence of the magnetic and transport properties of Co15Cu85 magnetic granular alloys (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3134-3138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of magnetic and transport properties of annealed Co15Cu85 alloys has been studied from 2 to 300 K. It was found that the magnetic property and resistivity significantly change with the temperature. Based on the two-current resistance model, we have calculated the electron spin-mixing parameter Q(T), which explains the magnetoresistance change with the temperature for granular Co15Cu85 alloys. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367070
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic properties and giant magnetoresistance in La0.67Ca0.33MnOx bulk material (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3191-3193 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and transport properties of a perovskite-type crystal sample with a nominal composition La0.67Ca 0.33MnOx have been investigated in the temperature range from 5 to 300 K with applied magnetic fields up to 5 T. Magnetization data obtained in the zero-field-cooled process exhibit the magnetic behavior with a Néel temperature, TN∼50 K and Curie temperature, TC∼300 K. The interesting feature in the temperature dependence of magnetoresistance is the appearance of a peak at T∼50 K, with value Δρ/ρ=[ρ(0)−ρ(5 T)]/ρ(5 T)=1300% at the Néel temperature, rather than at Curie temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115821
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