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  • 1
    Electronic Resource
    Electronic Resource
    Magnetization, Young's moduli, and magnetostriction of rare-earth–iron eutectic alloys with R=Tb0.6Dy0.4 : 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. 7009-7011 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rare-earth–iron alloys, R0.9Fe0.1, R0.72Fe0.28, and R0.42Fe0.58 (R=Tb0.6Dy0.4), containing the R/RFe2 eutectic composition were prepared by Bridgman and free-standing zone-melting techniques. Magnetization measurements were made in fields up to 800 kA/m between 55 and 300 K. A huge increase in magnetization below 210 K occurs as the R component becomes ordered. At low applied magnetic fields there is clear identification of both the ferromagnetic ordering temperature TC and the Néel spiral ordering temperature TN of R. (For Tb0.6Dy0.4, TC=165 K, TN=210 K.) Magnetization and magnetostriction measurements reveal very large magnetocrystalline anisotropies for both the R and the RFe2 components. Unexpectedly, at 77 K, were the rare-earth component of the eutectic system is ordered and the magnetostriction is large (λhγ(approximately-greater-than)0.6%), the magnetostriction is largest in the samples containing the largest amount of the RFe2 phase. Young's modulus measurements reveal the reduction in the stiffness with the addition of the softer rare earth to the stiff RFe2 compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358071
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic viscosity effects in the giant magnetoresistance of NiO/Permalloy/Cu/Permalloy exchange-biased films : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5218-5220 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have examined the effects of magnetic viscosity (magnetic aftereffect) on the giant magnetoresistance (GMR) of NiO/Permalloy(45 Å)/Cu(45 Å)/Permalloy(45 Å) exchange-biased spin-valve structures grown by direct current (dc) magnetron sputtering on Si substrates. One of the samples had a 6 Å Co layer on both sides of the Cu layer. GMR is a sensitive indicator of magnetic viscosity effects since any time dependence in the magnetization reversal of one of the layers is reflected directly in the GMR. Two different types of GMR measurements were made over the temperature range of −30 °C to 50 °C. The maximum time for the resistance to stabilize to 1 part in 104 ranged from about 70 to 200 s for both samples at the temperatures studied. The time dependency of the GMR was well described by C+S ln t, where S and C are constants; S is called the coefficient of magnetic viscosity. This equation characterizes the classic time dependent behavior of the magnetization. The maximum magnitude of S was found to decrease as the temperature was increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364472
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  • 3
    Electronic Resource
    Electronic Resource
    Multidomain and incomplete alignment effects in giant magnetoresistance trilayers : 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. 6525-6527 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The element specific magnetic hysteresis curves of Fe/Cu/Co trilayer structures can be used in conjunction with the measured magnetoresistance curves to extract the coefficient of the giant magnetoresistance (GMR) independent of magnetic domain effects and incomplete alignment effects, allowing for a measure of the maximum attainable GMR for that trilayer. Information concerning the details of the trilayer switching can be extracted showing that sputtered polycrystalline films of Fe/Cu/Co deposited on Si switch their magnetization directions like multidomain Ising magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358252
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  • 4
    Electronic Resource
    Electronic Resource
    Stress effect on the magnetization of Dy in the Dy/DyFe2 eutectic : 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. 7027-7029 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization of the alloy DyFe1.5 was studied as a function of temperature from 50 to 300 K in a range of magnetic field up to 10 kOe. Metallographic studies showed the existence of a eutectic phase containing both DyFe2 and elemental Dy embedded in the DyFe2 matrix. The presence of elemental Dy was observed in the magnetization data through a cusp in the temperature dependence of the magnetization at 178 K and an increase of the magnetization starting at 130 K and continuing to 80 K. While the first feature occurs at precisely the Néel temperature of bulk Dy, the second contrasts with the jump at the Curie temperature of 89 K observed in low fields in bulk single-crystal Dy. The more gradual increase in magnetization observed in the DyFe1.5 alloy is attributed to variations in stress to which the Dy is subjected. The temperature dependence of the magnetic moment from 80 to 130 K is modeled as arising from a collection of Dy particles of varying Curie temperatures. This variation is in turn caused by the stress distribution. Curie temperature distributions are found for a range of magnetic fields and then are extrapolated to zero field in order to eliminate the effect of field. The calculations indicate that a significant amount of the Dy remains in the helimagnetic phase down to zero temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358076
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  • 5
    Electronic Resource
    Electronic Resource
    Perpendicular transport and magnetic properties in patterned multilayer magnetic microstructures (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6084-6089 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using micron-level photolithography, we have prepared a set of patterned multilayer samples which have the form [Co/Cu/NiFeCo/Cu]×10 and which permit perpendicular current transport through the structure. Based on vibrating sample magnetometry, the multilayer stacks show a loss of ≈2 A(ring) of magnetic material at each interface. The magnetoresistance was measured as a function of temperature, magnetic layer thickness, and element size and the ΔR/R values range up to 8% at 300 K and 18% at 10 K. The thickness dependent data are modeled using an extension of existing methods and can be fit using comparable resistivity, interface resistance, and spin asymmetry parameters. The magnetic fringe fields of the elements have an important effect on the observed R vs H curves. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361892
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  • 6
    Electronic Resource
    Electronic Resource
    Factors affecting performance of NiO biased giant magnetoresistance structures : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6234-6236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have made spin-valve structures of Permalloy/Cu/Co by sputtering or electron-beam deposition onto the antiferromagnetic oxide NiO. The oxides were made either by deposition of the metals and subsequent oxidation or by growing them in situ using reactive sputtering. The magnetic properties of the giant magnetoresistance structures were studied by magnetoresistance, vibrating sample magnetometry, and ferromagnetic resonance methods. The oxides were characterized by x-ray diffraction and atomic force microscopy. We studied surface roughness and structure as functions of thickness and oxidation temperature and correlated the oxide properties with the magnetic performance. We found that the metal layer roughened during the postdeposition oxidation process and that the resulting oxide layers were very effective in pinning the direction of the magnetic moment of adjacent metal films. Coercive fields over 500 Oe were obtained for Co overlayers on NiO films but the exchange bias field was generally less than 100 Oe and was not strongly dependent on the roughness. The beneficial effects of this strong pinning were offset to some degree by higher switching fields required in spin-valve structures deposited over the Co. We also made reactively sputtered oxide antiferromagnetic films which had smoother surfaces than those made by postdeposition oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362079
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and magnetic studies of exchange bias films of Ir(20)Mn(80) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4927-4929 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of IrMn were made by magnetron sputtering, using nominally 20 at. % Ir, and their structural and magnetic properties were evaluated for use as an exchange bias material. The magnetic properties of different combinations of Py and CoFe underlayers were determined by magnetometry and by using ferromagnetic resonance (FMR) in the temperature range 4–350 K; x-ray analyses and atomic force microscopy were used to assess the structures. The IrMn films have the AuCu3 structure with strong 〈111〉 texture. The internal interfaces of the multilayer structures are very smooth. They induce relatively strong exchange bias in Py and CoFe overlayers but can have negligible coercivity. The bias field is strongly dependent on the direction of the moment during cooling, even well below 300 K, and coercivity and FMR linewidth increase with cooling. Isotropic shifts of FMR are small at 300 K but increase rapidly below 150 K. Our data suggest that spin-flop models for exchange bias may not apply to IrMn, and that small spin structures dominate low temperature behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373205
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  • 8
    Electronic Resource
    Electronic Resource
    Frequency and temperature dependence of ferromagnetic linewidth in exchange biased Permalloy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6901-6903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance linewidths were measured at 9.5 and 35 GHz and in the temperature range from 77 to 350 K for thin Permalloy (Py) films exchange biased by adjacent layers of NiO, CoO, or IrMn. Compared to unoxidized Py alone, for which the linewidth is nearly temperature independent in this range and scales linearly with frequency, exchange biased Py has broader lines with distinctive temperature dependences for each bias material at 9.5 GHz. Different temperature dependences were observed at 35 GHz. Our results are consistent with relaxation related to thermally driven reversal of the antiferromagnetic grains. Intrinsic damping and inhomogeneities also add to the widths. The qualitative features of the temperature and frequency dependences of the linewidths can be described with the usual expression for the slow relaxation linewidth mechanism. The temperature dependence of the relaxation time is taken from Néel's expression for the reversal time using appropriate rate prefactors and activation energies. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358824
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  • 9
    Electronic Resource
    Electronic Resource
    Andreev reflection: A new means to determine the spin polarization of ferromagnetic materials (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4589-4591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a simple method to measure the transport spin polarization of ferromagnetic materials. This technique relies on the fact that the Andreev reflection process at the interface between a superconductive and normal is influenced by the spin polarization P of the normal metal. In a very short time we have been able to measure the spin polarization of several metals: NixFe1−x, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2, whose spin polarization ranges from 35% to 90%. Our results compare well with other methods for measuring P. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370417
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic properties of R-Fe-B and R-Fe-Co-Al-B magnets (R=Pr and Nd) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5510-5512 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Permanent magnets based on the compositions Pr15Fe79B6, Nd15Fe79B6, Pr15Fe62.5Co16Al1B5.5, and Nd15Fe62.5Co16Al1B5.5 have been fabricated employing conventional powder metallurgical processes. Proper heat treatment has been found to improve magnetic properties. For example, in magnets of composition Pr-Fe-Co-Al-B, the heat treatment optimized in this study improved Br and (BH)max by about 5% and 10%, respectively, in comparison with conventional heat treatment reported in the literature. The temperature coefficients of magnetic properties have also been improved through Co and Al substitutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342319
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