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  • 1
    Electronic Resource
    Electronic Resource
    Substrate temperature effect on the structural anisotropy in amorphous Tb–Fe films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5785-5787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using extended x-ray absorption fine structures (EXAFS) measurements we have investigated the atomic environment around the Fe atom in a series of amorphous Tb0.26Fe0.74 films having different magnetic anisotropy energies owing to different deposition temperatures. The polarization properties of synchrotron radiation allowed the separate study of structure parallel and perpendicular to the sample plane. An anisotropy between these two structures was observed. Modeling results indicate this anisotropy is due to anisotropic pair correlations where the Fe–Fe pairs are statistically preferred in-plane and the Fe–Tb pairs out-of-plane. The amplitude of this anisotropy scales with both the substrate temperature and the magnetic anisotropy energy. A ≈1% in-plane compression of the Fe–Fe distance was measured between the in-plane and out-of-plane structure of the sample grown at 77 K. This sample had no detectable local chemical anisotropy suggesting that intrinsic stress plays an important role in determining its magnetic anisotropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353572
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrathin magnetic films of Fe/Ag(100): An approximate realization of a 2-d Heisenberg ferromagnet? (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5967-5967 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the transmission Mossbauer spectra of Fe/Ag(100) single crystal multilayers with large thicknesses (∼100 ML) of intervening Ag as a function of both temperature and magnetic field applied perpendicular to the surface. In contrast to earlier work on samples with less silver between layers, ordering temperatures are much reduced and the initial relaxation effects observed on cooling down appear to set in with a very small or zero order parameter.1,2 Measurements with a magnetic field applied perpendicular to the film surface showed a single well defined order parameter, which rules out superparamagnetizatism as the source of the observed relaxation effects. As an example, a sample measured earlier with 2.4 ML of Fe and 4 ML of Ag exhibited a well defined order parameter in zero field with a transition temperature near 200 K. In the present case a 3.0 ML Fe sample with ∼100 ML of intervening Ag exhibited relaxation effects setting in near 100 K, with a nonzero order parameter below ∼60–70 K. Measurements in a magnetic field showed clear evidence for long range spin–spin correlations even at temperatures above 100 K. Our interpretation is that for the films with relatively thin (∼4 ML) Ag layers between the Fe, there is sufficient coupling between layers to drive an essentially 3-d magnetic transition. With a very thick Ag interlayer separation, the characteristics of the film become much more like an ideal 2-d Heisenberg model, which builds up very long range spin–spin correlations at low temperatures, but whose actual magnetic ordering transition is depressed to T=0 (finite T with anisotropy).3 Presumably the transition which we estimate to be at 60–70 K is driven by the fact that the perpendicular anisotropy is not zero, but in fact is larger than the demagnetizing field.〈ks〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347833
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic properties of ferrimagnetic exchange-coupled rare earth-iron multilayered films : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6197-6199 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of magnetic and structural studies of sputtered and evaporated multilayers of Gd0.15Fe0.85 and Gd0.40Fe0.60 alloys. Using these alloy compositions, the net moment in each layer is antiferromagnetically aligned with the adjacent layers. The magnetic measurements were made at 300 K in a SQUID magnetometer with a maximum field of 55 kOe. The structures of the films were studied by large-angle x-ray diffraction and the compositions were checked with energy-dispersive x-ray fluorescence and Auger depth profiling. To first order, the magnetic behavior of these films can be described by a semiclassical model that treats the magnetization of each layer as uniform with an antiferromagnetic coupling to the adjacent layers. The necessity of using different parameters to fit the in-plane and perpendicular data indicates the existence of an anisotropy that is not included in this simple model. Spin-flop transitions, similar to those reported for multilayers of pure Gd and Fe are observed and are attributed to the antiferromagnetic exchange coupling at the interfaces. These films also display novel magnetic behavior that can be explained by enhancement of magnetostatic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349993
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  • 4
    Electronic Resource
    Electronic Resource
    Extended x-ray absorption fine structure studies of IBS Fe–Tb alloy films : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6311-6313 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have employed extended x-ray absorption fine structure (EXAFS) analysis to study the compositional dependence of the atomic structure in Fe–Tb alloy films. Fourier transforms of EXAFS data, relative to both the Fe K and the Tb LIII absorption edges, provide information about the local atomic environments relative to each atom. Results indicate the Fe EXAFS data to be dominated by Fe–Fe correlations, and consists of contributions from two Fe atomic shells at radial distances near 2.47 and 2.66 A(ring) and a Tb shell near 2.91 A(ring). The coordination number of the Fe shells are measured to increase, while radial distances decrease, with increased Fe content. The Tb EXAFS data was found to have an atomic shells of Fe and Tb at 2.91 and 3.47 A(ring), respectively. Analysis suggests that the Fe shell is very disordered and is comprised of approximately 9.5 atoms while the Tb shell has ≈3 atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349978
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  • 5
    Electronic Resource
    Electronic Resource
    Mössbauer study of 57Fe single-crystal films grown on (110) GaAs by MBE (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5646-5648 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed conversion electron Mössbauer spectroscopy measurements on a series of 57Fe (28–130 A(ring) thick) single-crystal films grown on GaAs(110) by molecular-beam epitaxy and overcoated with Al. The spectra were fit using a four-component model consisting of "bulk'' Fe (HHF =330 kG), a component with broad lines and reduced HHF (HHF =290 kG), corresponding to Fe with As, Ga, and Al in solid solution, a paramagnetic component (most likely corresponding to the Fe/Al interface), and a component corresponding to antiferromagnetic Fe2 As. For the thinnest film measured (30 A(ring)), the spectral areas of the components are approximately 44%, 36%, 5%, and 15%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345914
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    A miniature single element effusion cell for the vacuum deposition of transition-metal and rare-earth elements (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3168-3171 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A miniature single element effusion cell has been fabricated and tested that allows for the high-vacuum deposition of a variety of transition-metal and rare-earth elements. The cell is designed to operate under high-vacuum conditions, (approximate)10−9 Torr, with low power demands, 〈200 W. The virtues of this evaporator are the simplicity of design and ease of fabrication, assembly, maintenance, and operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148262
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  • 8
    Electronic Resource
    Electronic Resource
    Cation distribution in NiZn-ferrite films determined using x-ray absorption fine structure : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4561-4563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to study the cation distribution in a series of spin-sprayed NiZn-ferrite films, Ni0.15ZnyFe2.85−yO4 (y=0.16, 0.23, 0.40, 0.60). The Ni, Zn, and Fe EXAFS were collected from each sample and analyzed to Fourier transforms. Samples of Ni-ferrite, Zn-ferrite, and magnetite were similarly studied as empirical standards. These standards, together with EXAFS data generated from the theoretical EXAFS FEFF codes, allowed the correlation of features in the Fourier transforms with specific lattice sites in the spinel unit cell. We find that the Ni ions reside mostly on the octahedral (B) sites whereas the Zn ions are predominantly on the tetrahedral (A) sites. The Fe ions reside on both A and B sites in a ratio determined by the ratio of Zn/Fe. The addition of Zn displaces a larger fraction of Fe cations onto the B sites serving to increase the net magnetization. The fraction of A site Ni ions is measured to increase peaking at ≈25% for y=0.6. At higher Zn concentrations (y≥0.5) the lattice experiences local distortions around the Zn sites causing a decrease in the superexchange resulting in a decrease in the net magnetization. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361725
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  • 9
    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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  • 10
    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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