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  • 1
    Electronic Resource
    Electronic Resource
    Properties of melt-spun Co15Fe5Cu80, a bulk granular magnetic solid (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5540-5540 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the magnetic and transport properties of melt-spun Co15Fe5Cu80 as a function of heat treatment. Recently Xiao, Jiang, and Chien1 reported clustering and giant magnetoresistance in thin films of related alloys prepared by sputtering. We report qualitatively similar phenomena in these rapidly quenched ribbons. The unannealed samples exhibited saturation magnetoresistance of 0.2%. Annealing at 500 °C for 15 min in hydrogen increases the room temperature for magnetoresistance to 3%, and lowering the temperature to 77 K increased the magnetoresistance to 12.6%. Ferromagnetic resonance measurements at 35 GHz were also made. At room temperature the unannealed sample displayed a very broad resonance centered at 10 kG, consistent with a broad distribution of single domain particles of roughly spherical shape and an overall global magnetization 4πM=3.5 kOe. As the annealing temperature increases, the single domain particles with an inhomogeneous linewidth of ∼2 kOe grow into multidomain particles with a linewidth of ∼6 kOe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353642
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of local order in the amorphous precursor to Ba-hexaferrite thin-film recording media : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4890-4892 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ba-hexaferrite thin films for recording media applications are often fabricated by a two-step process: sputter deposition of an amorphous precursor, followed by annealing to crystallize the BaFe12O19 phase. The magnetic anisotropy of the crystalline films can be either in-plane or perpendicular, depending on the sputtering process used in the first step. However, conventional structural characterization techniques have not been able to distinguish between different as-sputtered films. Using polarization-dependent extended x-ray absorption fine structure (PD-EXAFS), we have observed anisotropic local structure around both Ba and Fe atoms in the amorphous precursor films. Comparison of the results suggests that the amorphous films consist of networks of Fe atoms surrounded by their O nearest neighbors, with Ba atoms fitting into in-between spaces as network modifiers (there might also be some minor Fe network modifying contribution). The local structural anisotropy of the amorphous films appears to determine the orientation of the fast-growing basal plane directions during annealing, and thus the directions of the c axes and the magnetic anisotropy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361641
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation of x-ray diffraction and Mössbauer effect measurements with magnetic properties of heat-treated Cu80Co15Fe5 ribbons : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6924-6926 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction (XRD) and Mössbauer Effect (ME) measurements were performed on heat-treated Cu80Co15Fe5 melt-spun ribbons in an attempt to understand the trends in magnetic properties with heat treatment. ME measurements indicate that the majority of Fe atoms (86%) occupy sites in ferromagnetic FCC CoFe clusters after the initial quench. A heat treatment at 900 °C acts to complete the chemical separation of Fe from the Cu matrix. The presence of Co in the Cu matrix, even after high temperature anneals, provides a paramagnetic component that prohibits saturation even at high fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356782
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and magnetism of multiphase Sm0.080Co0.645Fe0.276 powders : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5121-5123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Sm-poor mixture of Fe-substituted Sm2Co17, having the nominal stoichiometry of Sm0.080Co0.645Fe0.276, was ball-milled to explore the possibility of enhancing its remanence through direct microstructural refinement. With milling, the Sm2(Co0.7Fe0.3)17 compound disassociates to a body-centered-cubic supersaturated SmCoFe solid solution and a residual SmCoFe amorphous phase. Correspondingly, the coercive field values first increase, peaking at 0.83 kOe after 180 min of milling, then decrease with continued milling to 〈0.1 kOe after 1200 min. The remanence, as Mr/Ms, is measured to track closely the coercive field behavior, experiencing modest increases to 0.26 after just 120 min of milling. Magnetization values are found to increase first with the dissociation of the 2:17 phase, and again with the ejection of Sm from the bcc component. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365142
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  • 5
    Electronic Resource
    Electronic Resource
    Granular giant magnetoresistive materials and their ferromagnetic resonances (abstract) : 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. 6823-6823 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance (FMR) can reveal important information on the size and shape of the ferromagnetic particles which are dispersed in granular giant magnetoresistive (GMR) materials. We have investigated the FMR spectra of three different types of granular GMR material, each with different properties: (1) melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80, (2) thin films of Co20Cu80 produced by pulsed laser deposition, and (3) a granular multilayer film of [Cu(50 A(ring))/Fe(10 A(ring))]×50. We interpret the linewidth of these materials in as simple a manner as possible, as a "powder pattern'' of noninteracting ferromagnetic particles. The linewidth of the melt-spun ribbons is caused by a completely random distribution of crystalline anisotropy axes. The linewidth of these samples is strongly dependent upon the annealing temperature: the linewidth of the as-spun sample is 2.5 kOe (appropriate for single-domain particles) while the linewidth of a melt-spun sample annealed at 900 °C for 15 min is 3.8 kOe (appropriate for larger, multidomain particles). The linewidth of the granular multilayer is attributed to a restricted distribution of shape anisotropies, as expected from a discontinuous multilayer, and is only 0.98 kOe with the magnetic field in the plane of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358141
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy energy in single crystal Y1.8Er0.2Fe14B (invited) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3139-3139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There has been considerable interest in tetragonal R2Fe14B compounds as a basis for a new class of permanent magnet materials because of the unusually large energy products they exhibit at room temperature for certain rare-earth substitutions. The origin of the high-energy products is directly related to the large saturation magnetization and magnetic anisotropy energy. The magnetocrystalline anisotropy energy is believed to be directly related to an interaction between the 4f-electrons and the crystal field: however, to date few if any direct comparisons have been made between the experimental magnetic anisotropy and crystal field theory. The reason being that the large anisotropy energy makes it very difficult to use conventional torque magnetometry techniques to determine the angular dependence of the magnetic free energy, particularly at low temperatures where the higher-order terms become important. In this investigation we determine the angular dependence of the magnetic free energy as a function of temperature for Y1.8Er0.2Fe14B using high field (6 T) torque magnetometry techniques and make a direct comparison of the free energy with the energy calculated using a model based on crystal field theory. Y1.8Er0.2Fe14B was chosen because the Fe and Er sublattice anisotropy energies nearly cancel at low temperatures making it possible to measure anisotropy. Excellent agreement was obtained between the model and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340867
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties of R2Fe14B single crystals (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4091-4093 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A whole new class of high-performance permanent magnet materials is based on the ternary tetragonal structure R2Fe14B, where R is one of the rare-earth elements. We have successfully grown single crystals of this structure with R=Y, Nd, and Tb. Y is a nonmagnetic rare-earth substitute, while Nd and Tb couple ferro- and ferrimagnetically, respectively, relative to the iron moment. All three of the compounds have [001] easy axes at room temperature, although the Nd compound exhibits a spin reorientation away from the [001] below about 150 K. Nd2Fe14B has a saturation induction at room temperature of 16.2 kG, which places an upper limit of approximately 65.6 MGOe on the energy product obtainable by magnets based on that material. While Tb2Fe14B exhibits a smaller magnetization because of ferrimagnetic coupling of the rare earths and the iron, it also has an extremely large magnetic anisotropy which is nearly temperature independent between 4.2 and 300 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334681
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  • 8
    Electronic Resource
    Electronic Resource
    Phase-separated Fe and Co particles in a BN matrix (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3320-3322 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using co-sputtering, 10–300 A(ring) particles of Fe and Co have been prepared in an insulating BN matrix. The Fe particles have the α-Fe structure. The saturation magnetic moment of the iron particles per at. % Fe was found to be approximately independent of the Fe concentration and equal to the value of α-Fe. The system undergoes a metal–nonmetal transition at approximately 40 vol % Fe. For concentrations of Fe particles above this threshold the temperature dependence of the resistivity is metallic and the room-temperature coercivity is large (50–100 Oe). For the Co particles, the room-temperature coercivity is about twice as large as Fe above the metal–nonmetal threshold. Below the metal–nonmetal threshold the particles behave as superparamagnets and the coercivity is approximately zero.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338977
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  • 9
    Electronic Resource
    Electronic Resource
    Mössbauer study of spin reorientation in Y1.8Er0.2Fe14B (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3568-3570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe57 Mössbauer spectra were taken from 300 K down to 4.2 K for two single-crystal samples of Y1.8Er0.2Fe14B, one cut with its [001] axis normal to the surface, the other with its diagonal of [100], [010], and [001] axes normal to the surface. The former sample has shown that the angle between the Fe spin and the [001] increases continuously below ∼90 K. This qualitatively agrees with the spin reorientation (i.e., the easy axis of magnetization rotates away from the [001] toward [100] on cooling below ∼90 K) which have already been observed by torque magnetometry. The latter sample has shown that the Fe spin actually rotates continuously; abrupt change of Fe spin direction, which have been already suggested to occur in Er2Fe14B, does not occur in Y1.8Er0.2Fe14B. The samples were so thick that the intensity of strong absorption lines were saturated. We have derived a formula with which the saturation effect can be corrected in order to determine the angle of the Fe spin direction correctly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338728
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  • 10
    Electronic Resource
    Electronic Resource
    High-field torque magnetometry measurements on Y1.8Er0.2Fe14B (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3778-3778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y1.8Er0.2Fe14B is an interesting system in that the tendency of the Er ions to order in the basal plane is almost exactly canceled at low temperatures by the uniaxial anisotropy of the iron sublattice.1 We have performed torque magnetometry measurements in all three principal planes of a single crystal of this material at temperatures from 4 to 300 K in magnetic fields up to 60 kG, which is adequate to produce near saturation even in directions away from the principal axes, thus allowing us to determine the magnetocrystalline anisotropy free energy as a function of orientation and temperature. The free energy data were compared with calculations using the full set of crystal field parameters allowed by symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338640
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