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  • 1
    Electronic Resource
    Electronic Resource
    Susceptibility and magnetization processes in Sm2Fe17N3 powders (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6385-6390 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low field ac susceptibility and magnetization curves of milled Sm2Fe17N3 powders are measured for isotropic and aligned samples with average particle sizes ranging from 3.0 to 52 μm. Most of the particles are in a multidomain state before application of a magnetic field. The transverse ac susceptibility (χ⊥ac∼0.08) due to magnetization rotation against the anisotropy field is independent of particle size. The parallel ac susceptibility χ(parallel)ac and the susceptibility of isotropic powders are dominated by almost free domain wall movement in multidomain particles for which 〈χ〉=1.35. In very low fields (〈0.5 mT) χ(parallel)ac is small (∼0.1), but it increases toward a constant value of order 1 when the field exceeds a value of order 1 mT which is inversely proportional to the particle size. There is a corresponding increase in loss angle which is attributed to weak pinning of domain walls at surface defects. The volume fraction of single-domain and multidomain powder are deduced as a function of average particle size both in the unmagnetized and remanent states, from an analysis of high-field magnetization curves on isotropic powder. For example, about 87% of the volume of powder with an average size of 6.7 μm is multidomain in the unmagnetized state, but only 43% of the volume is multidomain in the remanent state. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363638
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  • 2
    Electronic Resource
    Electronic Resource
    Giant magnetostriction in amorphous (Tb1−xDyx)(Fe0.45Co0.55)y films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 973-977 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization and magnetostriction have been studied in amorphous (Tb1−xDyx)(Fe0.45Co0.55)y films. A well-defined easy axis is created by magnetic field annealing and the sperimagnetic cone structure, characteristic of these amorphous alloys, is reduced. The anisotropy has a minimum at x=0.73 as in the R Fe2 Laves phase. This points to the similarity between the local environments in the amorphous and crystalline states. A giant magnetoelastic coupling coefficient b of 60 MPa is developed at 300 K in low applied field for x=0, optimally annealed films. Assuming a Young's modulus and a Poisson ratio of 80 GPa and 0.31, respectively, the magnetostriction is evaluated at 1020×10−6. This is much larger than previously reported values in other amorphous films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360881
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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial growth and characterization of Y2Co17(0001) thin films deposited on W(110) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 997-1003 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y2Co17(0001) was grown on W(110) by pulsed laser deposition. The structural and morphological features of the films as a function of substrate temperature and thickness were studied in situ by means of reflection high-energy electron diffraction, and ex situ by means of scanning electron microscopy, transmission electron microscopy, and x-ray analysis (diffraction and reflection). Different growth modes were observed depending on the experimental conditions. They are discussed by considering the kinetical properties of the deposit and the thermodynamical properties of the system. The magnetic properties of the films have been investigated and related to the structural analysis. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360294
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic properties of amorphous nanocolumns created by heavy ion irradiation of paramagnetic YCo2 thin 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. 6661-6666 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent studies have demonstrated the possibility of inducing amorphous latent tracks in metallic materials by GeV heavy ion irradiation. In the present work, 0.880 GeV 238U beams have been used to induce ferromagnetic amorphous nanocolumns in nonmagnetic crystalline YCo2 films. The loss of crystallinity deduced by x-ray analysis is in good agreement with the one determined by magnetic measurements. The Co magnetic moment in the columns is approximately equal to 1 μB, as in bulk amorphous YCo2, but the ordering temperature (150 K) is strongly reduced with respect to the bulk. Magnetization measurements reveal the nanocolumns to be single domain. A perpendicular anisotropy is observed in samples irradiated at the smallest fluencies, which is interpreted to be due to shape anisotropy. A progressive decrease of the anisotropy with increasing fluence is observed and qualitatively described in terms of dipolar interactions between columns. At low temperature, the coercive field reaches 650 Oe. A simple nonuniform magnetization reversal process is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358161
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic viscosity in different Nd-Fe-B magnets (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3454-3456 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of magnetic viscosity in Nd-Fe-B magnets of different kinds (sintered magnets, MQII magnets prepared from ribbons, and LDC magnets prepared by liquid dynamic compaction) are reported. In all magnets, the viscosity S and the irreversible susceptibility χirr are found to be proportional. The temperature dependence of the coefficient Sv =S/χirr exhibits a sharp maximum at about 100 K. The temperature dependence of the activation energy E0 which governs magnetic aftereffects is deduced from these data. In sintered and LDC magnets, but not in MQII ones, E0 is found to be approximately proportional to the domain wall energy. It is concluded that the mechanism of coercivity is different in sintered and LDC magnets than in the MQII ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338751
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic behavior of Fe:Al2O3 nanocomposite films produced by pulsed laser deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6268-6274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structured nanocomposite films consisting of five Fe layers embedded in an amorphous Al2O3 matrix (Fe:Al2O3) have been grown by sequential pulsed laser deposition. The formation of well isolated quasispherical nanocrystals is observed for samples with Fe content per layer close to 6.5×1015 atoms/cm2. Increasing the Fe content leads first to the formation of elongated nanocrystals and then to quasicontinuous layers. The evolution in the shape and size of the nanocrystals is reflected in the magnetic behavior of these systems. A crossover from a low temperature ferromagnetic regime to a high temperature superparamagnetic regime is observed at a temperature of 23 K in the samples containing isolated quasi-spherical nanocrystals. In this case, a reduced moment per Fe atom (1.4 μB/atom) with respect to the value for α-Fe (2.2 μB/atom) is estimated. This behavior is attributed to the presence of a Fe-oxide surface shell on the nanocrystals. The large values of the estimated effective magnetic anisotropy (1.4×106 J/m3) and the low temperature coercivity in these samples are attributed to a strong surface contribution to anisotropy, whereas the temperature dependence of coercivity is attributed to thermal activation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415054
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of high-field magnetization measurements on R2Fe14B single crystals (R=Tb, Dy, Ho, Er, and Tm) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3713-3715 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystals of the compounds R2Fe14B some 1–4 mm in size have been grown for a study of the anisotropy of the magnetization curves. These curves for crystals with R=Tb, Dy, Ho, Er, and Tm were measured at the Service National des Champs Intenses, Grenoble, between 4.2 and 275 K, with fields of 0–18 T being applied along the [100], [110], and [001] directions. Magnetization curves for all five compounds are analyzed in terms of the exchange and crystal field interactions (including terms up to sixth order, which may differ at 4 f and 4g sites) following the analysis previously developed for Nd2Fe14B. Molecular field coefficients representing the exchange interactions between R and Fe spins decrease from light to heavy R compounds as previously deduced from analysis of Curie temperatures. The CEF parameters are approximately the same across the series. In particular, the A20 terms are constant to within 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340644
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  • 8
    Electronic Resource
    Electronic Resource
    50 T pulsed magnetic fields in microcoils (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1996-2002 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we present a system based on microcoils capable of generating pulsed magnetic fields up to 50 T. We discuss the current generation and the measurement techniques currently used. We have measured the Faraday rotation for different paramagnetic materials, glass, gadolinium gallium garnet, Pr gallium garnet, and Si and have used the results to calibrate the magnetic field achieved. We discuss the relative merits of such a system compared to conventional ones, as well as the field characteristics obtained. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372126
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  • 9
    Electronic Resource
    Electronic Resource
    Angular dependence of coercivity in sintered RFeB magnets : 35TH ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS San Diego, California (USA) 29 Oct−1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5492-5494 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The angular dependence of the coercive field Hc(cursive-theta) is discussed as a means of studying magnetization reversal in permanent magnets. We consider Hc(cursive-theta) for permanent magnets RFeB (R=Pr, Nd) for temperatures between 4.2 and 300 K. At high temperatures, it is found that Hc may increase by a factor 1.5–2 as cursive-theta increases from 0 to π/2. At low temperatures, in the Pr magnets, Hc decreases as cursive-theta increases from 0 to π/4 and then increases for larger angles. Different possible mechanisms for magnetization reversal are considered and the associated angular dependences of the coercive field in single crystals are calculated. The corresponding Hc(cursive-theta) are deduced for permanent magnets from the grain orientation distribution. Better agreement with experimental data is obtained in models involving domain-wall propagation and leading to a 1/cos cursive-theta dependence, or close to it, than in models involving coherent rotation. The behavior of the PrFeB magnets is not explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347977
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetization processes in amorphous R-Co/R'-Co/R-Co sandwiches (R, R'=Y, Nd, Gd, Er) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5677-5679 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sandwiches consisting of three amorphous layers (R0.33,Co0.67)1000 A(ring)/ R'0.33,Co0.67)1000 A(ring)/ (R0.33Co0.67)1000 A(ring), have been prepared by dc triode sputtering (R, R' are rare-earth elements). The systems chosen are such that the bulk magnetization alternates from one layer to the next or the coercivity of each layer is significantly different. Magnetic transitions are observed under field. They have been quantitatively analyzed in terms of successive reversals of magnetization in the different layers. The creation or annihilation of planar Bloch walls parallel to the surface are associated with the magnetic transitions. The wall energy and wall width depend essentially on the competition between exchange energy and Zeeman energy. It is suggested that the existence of such Bloch walls may favor magnetization reversal in thin films by coherent processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345924
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