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  • 1995-1999  (27)
  • 1
    Electronic Resource
    Electronic Resource
    Microstructure and composition in rapidly quenched NdFeB-based hard magnet alloys : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4848-4850 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of the microstructure and composition in hot-pressed (MQ-2) and die-upset (MQ-3) magnet alloys based on the Nd2Fe14B composition, utilizing high resolution and analytical transmission electron microscopy, is reported. The initial magnetic properties of the two samples show different behaviors, which are attributed to the difference in the anisotropy of the grain structure and the grain boundaries. The hot-pressed sample shows faceted grains of the 2-14-1 phase, while die-upset sample shows plate-like grains, together with larger equiaxed grains that contain a speckling of precipitates in the grain interior. The grain structure and composition remain rather similar in the two samples. The grain boundary phase averages ∼1–(approximately-greater-than)10 nm in width. The thicker grain boundaries are Nd-rich, while the thinner grain boundaries in the hot-pressed sample exhibit an Fe-rich composition near that of the NdFe3 phase. Nd-rich phases are found at the grain boundary junctions of both samples, with the Nd:Fe ratio near 7:3 in the die-upset sample, and up to 3:2 in the hot-pressed sample. The significance of the microstructure and the grain boundary phases on the magnetic behavior in the two samples is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361630
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  • 2
    Electronic Resource
    Electronic Resource
    Epitaxial Fe16N2 films grown on Si(001) by reactive sputtering : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5321-5323 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a crystallographic template for the growth of the range of Fe-N phases on Si(001) by lattice matching on selected underlayers. Epitaxial films of pure α-Fe, γ′-Fe4N, and α′-Fe8N (N martensite) were grown individually by the optimization of reactive N2 sputtering parameters. The orientation relation of the Fe-N phases was Fe-N(001)(parallel)Ag(001)(parallel)Si(001) and Fe-N[100](parallel)Ag[110](parallel)Si[100]. Annealing the α′-Fe8N films resulted in the formation of α′-Fe8N/α″-Fe16N2 mixtures. In addition to the crystallographic and structural analysis, quantification of x-ray diffraction peak intensities confirmed that the α′/α″ mixtures contained as much as 46 vol % α″ (remaining α′). Vibrating sample magnetometry and SQUID magnetometry measurements of the α′ and α′(54%)/α″(46%) mixture, respectively, indicate enhanced magnetic moments for both the α′ and α″ phases with respect to pure Fe. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361365
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  • 3
    Electronic Resource
    Electronic Resource
    Role of epitaxy and polycrystallinity in the magnetoresistance and magnetization of La0.8Sr0.2MnO3 thin films : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5169-5171 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: La0.8Sr0.2MnO3 thin films were simultaneously deposited by pulsed laser ablation on silicon (Si) and LaAlO3 (LAO) substrates. Films on Si were polycrystalline while those on LAO were (100) epitaxial with an in-plane correlation length of ≈10 nm. The magnetization and magnetoresistance behavior of these two films were significantly different. Both films exhibit antiferromagnetic–ferromagnetic transitions—at different temperatures [180 K (LAO); 230 K (Si)]—and their magnetic moments at 10 K were significantly different (Si—0.0035 emu; LAO—0.0022 emu). However, both films showed significant high field slope in magnetization at 10 K. Significant fractions of both films remain antiferromagnetic at low temperatures and hence net susceptibilities, dependent on the direction of the applied magnetic field, are different for the epitaxial (LAO) and randomly oriented polycrystalline (Si) films. The magnetoresistance peak, corresponding to the semiconductor–metal transition is observed at 170 and 130 K for the epitaxial (LAO) and polycrystalline (Si) films, respectively. Moreover, their resistance values are two orders of magnitude different (Si—MØhms; LAO—KOhms). These properties can be interpreted in terms of the major role of grain boundaries in determining the scattering as well as possible differences in O2 stoichiometry. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361919
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  • 4
    Electronic Resource
    Electronic Resource
    Plasma distribution of cathodic arc deposition systems (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6785-6790 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma distribution using a cathodic arc plasma source with and without magnetic macroparticle filter has been determined by depositing on a transparent plastic substrate and measuring the film absorption. It was found that the width of the distribution depends on the arc current, and it also depends on the cathode material which leads to a spatial separation of the elements when an alloy cathode is used. By applying a magnetic multicusp field near the exit of the magnetic filter, it was possible to modify the plasma distribution and obtain a flat plasma profile with a constant and homogeneous elemental distribution which was demonstrated by depositing FeNd thin films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361523
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic and physical microstructure of Fe16N2 films grown epitaxially on Si(001) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4128-4130 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Fe16N2 films were grown on Si(001) substrates with an Ag underlayer by reactive sputtering in nitrogen. Pure α′-Fe8N films were obtained which on subsequent annealing resulted in mixtures of α′-Fe8N (54%) and α′′-Fe16N2 (46%). An average moment of 1780 emu/cc, considerably larger than that of pure α-Fe (1714 emu/cc), was measured for both samples. Plan-view transmission electron microscopy of the films confirms the orientation relationship Fe16N2(001)||Ag(001)||Si(001) and Fe16N2[100]||Ag[110]||Si[100], and a small grain size (∼100 Å), while electron energy-loss spectroscopy confirms an average composition of Fe8N for both samples. Electron diffraction patterns indicate that the as-deposited α′ films already contain very small regions of ordered α′′ which were not previously detected by x-ray diffraction measurements. Mössbauer spectroscopy performed at both 300 and 16 K gave three hyperfine fields corresponding to three different iron sites for both the unannealed α′ and the annealed α′/α′′ mixtures. Lorentzian fitting of the three iron components for the α′/α′′ spectrum obtained at room temperature gave an intensity ratio of 1:2:1 (FeI:FeII:FeIII) corresponding to the expected occupancy for the three Fe sites in the Fe16N2 structure. Moreover, the pure α′ film at 300 K and both samples at 16 K showed deviation from this distribution. The three components show notable differences in the temperature dependence of their occupancies; however, all three magnetic components deviate similarly from the surface normal. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365102
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  • 6
    Electronic Resource
    Electronic Resource
    Quenching of giant magnetoresistance by interface roughening and alloying in annealed [(NixFe1−x)yAu1−y]/Au multilayers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1963-1965 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Antiferromagnetically coupled permalloy/Au multilayers display giant magnetoresistance (GMR) with large changes in resistance in very low fields. We show that thermal annealing of such structures, exhibiting GMR, leads to a quenching of the magnetoresistance. The detailed structure of the permalloy/Au interfaces has been probed using high-resolution cross-section transmission electron microscopy. On annealing, the Au layers interdiffuse into the permalloy layers, which leads both to rougher permalloy/Au interfaces and to "thinner'' Au spacer layers. We infer that the latter results in ferromagnetic coupling of the permalloy layers, which accounts for the reduced GMR. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117636
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  • 7
    Electronic Resource
    Electronic Resource
    Unusual substitutional properties of Ru in the La0.7Sr0.3Mn1−xRuxO3 system : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7183-7185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: La0.7Sr0.3Mn1−xRuxO3, 0≤x≤0.2 samples were prepared both in bulk and thin film formed using pulsed laser deposition. Magnetization measurements of bulk samples indicate a marginal decrease in Tc from 366 to 335 K up to 15% Ru substitution in Mn site. X-ray diffraction of the 〈100〉 oriented epitaxial films indicate a monotonic increase in the lattice parameter with Ru doping. The magnetoresistive behavior of the Ru substituted films are comparable with the parent La0.7Sr0.3MnO3 films. Unlike other elemental substitution in Mn sites, the effect of Ru to stabilize magnetic ordering at elevated temperatures is exceptional. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367630
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  • 8
    Electronic Resource
    Electronic Resource
    Evolution of strain-dependent transport properties in ultrathin La0.67Sr0.33MnO3 films : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7073-7075 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a systematic investigation of strain-induced lattice distortion effects on the crystal structure and transport properties of as-grown and postannealed ultrathin La0.67Sr0.33MnO3 epitaxial films grown on LaAlO3 (001) substrates by pulsed laser deposition. The resistivity of the as-grown films is critically dependent on the thickness, i.e., 100 Å thick films show insulating behavior, 300 Å thick films show metal-insulator transitions, and 500 Å thick films show metallic behavior. However, all the annealed films show identical metallic behavior. Conventional θ–2θ x-ray scans with momentum transfer (q) along the [001] direction, and θ–2θ scans of the (103) and (113) peaks, with q having a component perpendicular to the growth direction, were used to measure the out-of-plane and in-plane lattice parameters of the sample. Φ scans of the (103) and (113) peaks revealed a fourfold symmetry which is consistent with a tetragonal unit cell. These data conclusively show that significantly elongated tetragonal structures (c/a=1.02–1.04) are insulating whilst films with cubic unit cells, relaxed either due to annealing or as a function of thickness, have metallic characteristics. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367864
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  • 9
    Electronic Resource
    Electronic Resource
    Exchange biasing of permalloy films by MnxPt1−x: Role of composition and microstructure : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6810-6812 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interfacial coupling energy, Δσ for polycrystalline Ni0.8Fe0.2 (100 Å)/MnxPt1−x (t Å)/SiO2 bilayers, has been determined from wedge samples spanning a MnxPt1−x composition range 0.42〈x〈0.76 and t∼350 Å. Δσ exhibits a sharp peak of 0.1 erg/cm2 at 51% Mn. We compare the magnetic and microstructural properties of two bilayer films, which have the same compositions of permalloy and MnxPt1−x: [Ni0.85Fe0.15(100 Å)/Mn0.49Pt0.51(t Å)]. In one case (normal structure), the epitaxial permalloy was grown first onto Pt/MgO(001), followed by 170 Å of Mn0.49Pt0.51. In the other structure (inverted), a 350 Å thick polycrystalline film of Mn0.49Pt0.51 was grown onto a SiO2 substrate, followed by permalloy. The structures exhibited very different exchange bias fields (32 versus 86 Oe) and Δσ values (0.021 versus 0.060 erg/cm2), respectively. Significant differences in texture, grain size, and Mn0.49Pt0.51 layer thickness for the two samples are reported. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367815
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  • 10
    Electronic Resource
    Electronic Resource
    Enhanced saturation magnetization, electronic structure, and compositional segregation in epitaxially grown Co–Cr thin films (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2238-2240 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used the recently established linear correlation between the total intensities of the L3,2 "white lines'' in electron energy-loss spectroscopy and the number of unoccupied 3d states to probe the local electronic structure in epitaxially grown Co–Cr thin films. The significant enhancement of saturation magnetization measured for these epitaxial films, when compared to homogenized bulk alloys, has been correlated directly to the unoccupied 3d states to the Co atoms in these materials. These measurements are the first direct electronic structure evidence that may support models associating the enhancement of saturation magnetization with intragranular segregation in Co–Cr thin films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115115
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