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  • 1
    Electronic Resource
    Electronic Resource
    Effect of refractory additives on coercivity of sintered (Nd, Dy)(Fe, Co) BM magnets (M=Cr/W/Zr/Nb/Ta) (abstract) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6375-6375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a trial to develop heat-resistant sintered Nd2Fe14B magnets, a refractory element (Cr/W/Zr/Nb/Ta) was selected as an additive incorporating Dy and Co in the Nd-Fe-B composition. Nd13Dy1.5Fe72−xCo6B7.5Mx alloys (M=Cr/W/Nb/Ta, x=0, or 3.5) were arc-melted, pulverized, compacted, and sintered by the conventional powder metallurgy method. It was found that W/Cr greatly enhances the as-sintered intrinsic coercivity (iHc, in kA/m), e.g., from 510 (x=0) to 810 (W, x=3.5) or 740 (Cr, x=3.5). An additional two-stage annealing at 900 and 600 °C for 1 h each led to an even higher iHc of 1000 (W, x=3.5). While Nb/Ta moderately enhanced as-sintered iHc, and responded less to additional annealing. Temperature coefficients of remanence was found to be greatly improved by the W or Cr addition, e.g., 0.43%/°C for x=0 and 0.06%/°C for M=W, x=3.5 (p=1, 20–150 °C). They are thus very suitable for applications at temperatures up to 150 °C. EPMA analyses showed the possible existence of a M2FeB2 (M=W/Nb/Ta) phase at grain boundaries. Thermomagnetic analyses and detailed microstructure of the sintered and/or annealed magnets are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349947
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  • 2
    Electronic Resource
    Electronic Resource
    High-performance sintered R2Fe14BNx (R=Nd/Pr/Dy) magnets : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6600-6602 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-performance R2Fe14BNx-type magnets (R=Nd and/or Pr/Dy) were successfully prepared by sintering. The optimum magnetic properties are coercivity iHc: 680–1440 kA/m; Hc: 500–1000 kA/m; Br: 1.0–1.3 T; and (BH)m: 180–250 kJ/m3 depending on the composition and processing parameters, especially the proper sintering conditions, including nitrogen intake at 1040 to 1050 °C. The magnets thus obtained have Tc values of 335 to 370 °C depending on the nitrogen content, which should be 〈6 at. % for thermal stability. The anisotropy field increases from 6.2 to 8 T with addition of nitrogen, and magnetization measured at 2 T increases by 18%. The weight loss after immersion in a 5% HCl solution for 30 min is 25% less for nitrogenated magnets than for those without nitrogen, due to the replacement of the Nd-rich phase at grain boundaries by more corrosion- resistant nitrides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349870
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  • 3
    Electronic Resource
    Electronic Resource
    High coercivity melt-spun Nd10–11.5Fe82–84B2–5M1–6 alloys (M=Ti/V/Mo/Al) (abstract) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6376-6376 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In an alloy design to precipitate the hard Nd2Fe14B (2-14-1) in the NdFe11M (1-12 phase, M is one of Ti/V/Mo/Al) matrix, different ratios of the 2-14-1 composition were added into the 1-12 compositions and prepared by melt spinning. It resulted in high-coercivity Nd-Fe-B-M alloys (M is Ti/V/Mo/Al) with Nd and B composition less than the stoichiometric 2-14-1 compound, yet with promising intrinsic coercivity (iHc) of up to 12 kOe after suitable annealing. XRD analyses showed that for the alloys with higher iron lower in both Nd and B, the matrix is 1-12 and alpha-iron, while for the alloys with higher Nd and B, the 2-14-1 is competitive with other phases. The iHc vs temperature fitting of a Nd10Fe83.1B2.7Ti4.2 alloy (iHc=80 kA/m at 293 K) shows weak pinning, while that of a Nd10.8Fe82.9B4.4Ti1.9 alloy (iHc=900 kA/m at 293 K) shows strong pinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349948
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of nitridation on magnetic properties of Fe53Pt47 thin film (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3145-3149 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Fe53Pt47 thin films with varying thickness were prepared using dc magnetron sputtering at various substrate temperatures (i.e., from 250 to 600 °C) on to CrMo seeded glass substrates. The powder x-ray diffraction studies reveal that the ordered fct γ2-FePt phase begins to appear starting from the substrate temperature of 250 °C. The estimated ordering parameters show that the films prepared at 300 °C are well ordered and ordering parameters increase slowly as increasing substrate temperatures. On nitridation of the Fe53Pt47 thin films, expansion of the face centered tetragonal crystal lattice along the c axis is observed. The saturation magnetization is decreased with decreasing film thickness. This has been explained mainly on the basis of size and surface effects of nanocrystals in the films including intergranular interactions. Maximum coercivity of 8.7 kOe is observed for the film thickness of 350 nm. The drastic decrease in magnetization with the increase in nitridation time duration has been attributed to the spin pairing effects as a result of electron supply from interstitial nitrogen atoms to the 3d bands of iron atoms. We observed an increase of Hc from 7.8 kOe for non-nitrided Fe53Pt47 film to 10.8 kOe for a 3 h nitrided film. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1436301
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  • 5
    Electronic Resource
    Electronic Resource
    Optical properties and structure of tellurium–germanium– bismuth–antimony compounds with fast phase-change capability (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3290-3294 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quaternary TeGeBiSb amorphous films, 100 nm in thickness, were prepared by rf sputtering onto either a Si (100) or polycarbonate substrate. Crystalline films were obtained by subsequent annealing at 300 °C for 10 min. At least two phases with hexagonal and rhombohedral structures were identified by x-ray diffractometry in the quaternary system. Their compositions are close to formulas Te5Ge4Bi4Sb and Te5Ge4Bi7Sb, with c/a ratios of 5.5 and 9.4, respectively. The Te5Ge4Bi4Sb film shows a reasonable reflectivity contrast ranging from 20% to 25% in the whole visible spectrum, while the reflectivity contrast of Te5Ge4Bi7Sb film shows a sharp lowering tendency with decreasing wavelength and turns negative at wavelengths smaller than 470 nm. Results of thermal analyses show that the films crystallize at around 236–266 °C with corresponding activation energies 2.67–2.88 eV. The change in reflectivity contrast is explained based on the variation in optical band gaps of the TeGeBiSb materials with either Bi content or annealing temperature. These materials may find applicability in reversible type phase-change optical recording. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1348327
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  • 6
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance enhancement in spin valves with nano-oxide layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6928-6930 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetoresistance (MR) ratio is enhanced by 35% by inserting the nano-oxide layer (NOL) at the Ta/Co interface in the FeMn-based top spin valves (Ta/NOL/Co/Cu/Co/FeMn/Ta). The enhancement is attributed to specular reflection, resulting in a large resistance change and small sheet resistance. However, the formation of NOL at the interface of Ta/Co suppresses the (111) texture, resulting in small exchange fields. Top spin valves with NOLs show good thermal stability up to 200 °C annealing. The MR ratio is further increased after annealing at temperatures below 200 °C. Enhancement of the MR ratio by 61% can be achieved by annealing at 150 °C. For bottom spin valves (Ta/NiFe/FeMn/Co/Cu/NiFe/Ta), NOLs formed at FeMn/Co and NiFe/Ta interfaces increase MR ratios, but NOLs at Co/Cu or Cu/NiFe deteriorate the differential spin scattering and significantly reduce MR ratios. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356717
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties of sputtered Fe1−xO and Fe+Fe3O4 thin films : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5250-5252 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An attempt was made to increase saturation magnetization of Fe3O4 films by incorporating α-Fe phase through the decomposition of as-deposited Fe1−xO films, which were dc-sputtered onto Si(100) substrate by controlling the oxygen flow rates to a thickness of 70–400 nm. The as-prepared Fe1−xO films, being ferrimagnetic, show a thickness dependent microstructure and properties. The formation region of the single phase Fe1−xO was worked out as functions of oxygen flow rate and thickness. After vacuum-annealing, the Fe1−xO phase decomposed to Fe+Fe3O4 phases leading to an increase in coercivity from 15 Oe to 520–990 Oe, and an increase in saturation magnetization from 100 to 290–410 emu/cm3 depending on film thickness. The nanostructure of as-prepared and annealed films were examined by a high resolution transmission electron microscope, the former does not show well defined grain boundaries, while the later has well defined grains, 20–50 nm in size. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364483
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  • 8
    Electronic Resource
    Electronic Resource
    Nanocomposite Sm2Co17/Co permanent magnets by mechanical alloying : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5964-5966 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mechanically alloyed magnets SmCox (x=6.0–11.0) have been prepared using starting materials of commercial SmCo5 and Co powders. X-ray diffraction data indicate that the equilibrium Sm2Co17 phase can be achieved in a nanocomposite Sm2Co17/Co system at x=8.5–11.0, while a Sm2Co17/SmCo5 structure occurs at x=6.0–8.0. The best magnetic properties obtained at x=10.0 are as follows: (BH)max=10.2 MGOe, Br=9.4 kG, Hc=4.0 kOe, and S=0.82. Wohlfarth's remanence analysis indicates that the high remanence can be attributed to the intergranular interaction between neighboring cobalt and Sm2Co17 grains. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362121
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  • 9
    Electronic Resource
    Electronic Resource
    Coercivity of Ti-modified (α-Fe)-Nd2Fe14B nanocrystalline alloys : 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. 7071-7073 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coercivity of Ti-modified nanocrystalline (α-Fe)-Nd2Fe14B alloys with soft iron particles embedded in hard Nd2Fe14B matrix was studied. The alloys were prepared by melt spinning and annealing. The grain size of Nd2Fe14B is from 20 to 60 nm, while that of the soft iron particles is 11 to 30 nm. The coercivity of the annealed flakes decreased dramatically with increasing particle size of free iron, following the same tendency of a theoretical calculation by Schrefl et al. For the Ti-alloyed flakes, the 1 at. % Ti-containing ones show the highest coercivity of 11.1 kOe. Its (BH)m value is about 16 MGOe despite lower Nd and B contents than stoichiometric Nd2Fe14B. More Ti addition would deteriorate the coercivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358030
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  • 10
    Electronic Resource
    Electronic Resource
    Anomalous perpendicular magnetoanisotropy in Mn4N films on Si(100) : 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. 6582-6584 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferrimagnetic Mn4N films were deposited on Si (100) substrate by dc reactive magnetron sputtering from sintered Mn target. Highly (002) textured Mn4N ordered phase is formed in situ at studied substrate temperatures of 150–250 °C without further annealing. Anomalous perpendicular magnetoanisotropy exists in these face-centered cubic films with larger coercivity measured perpendicular to the film (2000–3000 Oe) than that parallel (1100–1300 Oe), as is the remanence. Coercivity in either direction decreases, while the saturation flux density (from 240 to 610 G) increases with increasing substrate temperature. The anomalous perpendicular magnetoanisotropy is attributed to (1) the stress-induced anisotropy due to in-plane tensile stress coupled with a reverse magnetostriction, and (2) the shape anisotropy due to columnar grain structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358200
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