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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5417-5419 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Critical points and lines in magnetic field space define the boundaries of different magnetization states between which the magnetization may "jump," leading to hysteresis. We calculate the changes in these boundaries due to magnetoelastic coupling to applied stresses, and obtain the critical stresses required to eliminate jumping in specific cases. These results may provide a way of reducing or eliminating hysteresis in large magnetostriction materials. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6216-6218 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of Young's modulus has been measured for a series of Tb1−xDyxZn pseudobinary compounds with x ranging from 0 to 1. From the sharp dips in the modulus vs temperature data, the reorientation transition temperatures have been determined, and the magnetic phase diagram deduced. Magnetization measurements taken on the same samples show less pronounced features at the corresponding temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7027-7029 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4413-4415 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study is made of the stability of ferromagnetic long-range order under fluctuations due to random easy magnetic axes, including the dipole–dipole coupling. This coupling produces two effects. There is a random dipole field that acts on the spins in the same way as does the random uniaxial anisotropy. Secondly, there is an average dipole field that acts to prevent the appearance of spin-density gradients. The net result is very dependent on the number of spin components. For the planar model in three dimensions, there is a logarithmic divergence of the magnetization reversal and power-law spatial dependence of the correlation function. Thus the lower critical dimension is reduced from four to three by the presence of dipole interactions in the planar (x-y) version of the random easy axis model. For the Heisenberg model the random magnetic anisotropy destroys the long-range ferromagnetic order. There is a correlation length that depends on the direction of the local magnetization. Results of a calculation of the spin–spin correlation function are used to predict qualitatively different ordered regions (domains) for small random anisotropy as compared to large random anisotropy.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6250-6252 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization, magnetostriction, and elastic modulus measurements were made on single crystal specimens of Tb1−xDyxZn. Easy axis magnetization rotation as much as 26° were observed in the (001) plane of Tb0.75Dy0.25Zn below 33 K. From these measurements, values of the K4/K8 anisotropy ratios were calculated. No easy axis magnetization rotation was observed in the x=0.6 and x=0.8 single crystals. Magnetostriction and modulus measurements at 77 K in Tb0.4Dy0.6Zn showed a saturation magnetostriction of ∼5×10−3 and a maximum magnetomechanical coupling factor of 0.96. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3644-3646 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mössbauer effect measurements were obtained on smooth-surface Fe78B13Si9 amorphous ribbons annealed in a transverse magnetic field at high temperature. Absorption spectra were obtained with the ribbon plane tilted at several angles with respect to the direction of the γ rays, in an external field ranging from 0 to 10 Oe. Intensity ratios were analyzed to obtain the magnetization as a function of field. A large zero-field spread was deduced and excess scatter near the anisotropy field was observed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5792-5794 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the free energy of a crystal field model designed to reproduce the magnetic temperature, composition phase diagram for Tb1−xDyxZn alloys. Using fourth- and sixth-order coefficients consistent with single-ion theory, it was found to be impossible to reproduce the experimental phase boundaries. A reasonable fit to the entire diagram was obtained when the coefficients were chosen to be of the same sign for Dy and Tb, rather than of opposite sign, as required by single-ion theory. To explain this discrepancy, a model is introduced which includes a contribution to the crystal field coming from quadrupole–quadrupole interactions. It is argued that the reason for the success of the calculation using coefficients of the same sign is directly related to the dependence of the strength of the quadrupole coupling on the square of the second-order Stevens factor. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5733-5735 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitrogenation process of the TbFe3 intermetallic compound was studied by heat treating the alloy between 573 and 873 K in a nitrogen atmosphere. The structural and magnetic properties of the nitrogenated samples were characterized by x-ray diffraction (XRD), Mössbauer spectroscopy, and magnetic measurements. The magnetic moments of the nitrogenated samples were found to be a function of the annealing temperature and showed a minimum for the sample heat treated at 673 K. The XRD pattern of this sample (673 K) showed that the Bragg peaks of the 1-3 phase had completely disappeared and were replaced by a broad maximum indicating a breakdown of the TbFe3 structure into an amorphous phase. The room-temperature Mössbauer spectrum of the same sample consisted almost entirely of a quadrupole-split doublet plus a small amount of α-Fe and TbFe3. This doublet split into a broad spectrum upon cooling which is typical of amorphous rare-earth–transition-metal compounds. For samples heat treated at higher temperatures, the amount of α-Fe and TbN phases gradually increased. This nitrogenation process is unlike that of R2Fe17. In this study, nitrogen atoms do not go into the interstitial sites. Instead, they create a ferromagnetic (TC≈215 K) amorphous phase of Tb, Fe, and N which is stable over a wide temperature range.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5981-5983 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We consider the effect of random surface roughness on a semi-infinite ferromagnetic film. We calculate the magnetization as a function of distance from the surface and the spin-spin correlation as a function of lateral separation. We show that, even in the absence of crystalline anisotropy or an external field, the surface of the ferromagnet is stable against random torques created by the roughness. Near the surface, the magnetization reduction is inversely proportional to the square of a "healing'' length λ0≡(D/2πM0)1/2, where D is an exchange stiffness and M0 is the saturation magnetization. The correlations in fluctuations of the magnetization orientation decay exponentially with distance parallel to the surface, λ0 being in the exponent. In contrast, fluctuations decrease only as the reciprocal of the square of the distance perpendicular to the surface. Results are discussed and compared with other calculations of the effects of random surface perturbations.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5879-5879 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent magnetoresistance experiments1,2 on Fe/Cr/Fe sandwiches and superlattices show that the critical magnetic field for saturation varies linearly with temperature from liquid helium to room temperature. The drop in critical field is as large as 30%, even though the reduction in Fe magnetization is negligible over this temperature range. In order to gain some insight into the physical origin of this softening of the critical field, which is a measure of the antiferromagnetic interlayer coupling, we have studied a phenomenological model of an Fe/Cr/Fe sandwich structure which consists of two Fe films coupled at their interface by an antiferromagnetic exchange at zero temperature. The Fe films themselves are ferromagnetic and subjected to an external field and uniaxial in-plane anisotropy. The Fe spins are confined to the film plane. The temperature dependence of the critical field, i.e., the field below which the spins in the two films deviate from the direction of the field, arises from fluctuations in these spin deviations, which are present for any temperature greater than zero. Using an approximation in which these fluctuations are treated classically, the critical field decreased linearly with temperature, with a coefficient that increases logarithmically with the transverse dimension of the films. Interpreting this length to be of the order of the grain size in polycrystalline films or a coverage terrace width in epitaxially grown material, we can directly relate the temperature variation of the antiferromagnetic interaction to film quality. The larger this dimension, the greater the decrease of the coupling with temperature; hence, "better'' films are expected to show weaker (or zero) coupling at room temperature. Conversely, the magnetization of the Fe films is not critically dependent on this dimension. Extension of the model to include spin-wave effects will be discussed.
    Type of Medium: Electronic Resource
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