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  • 2000-2004  (10)
  • 1985-1989  (15)
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  • 1
    Electronic Resource
    Electronic Resource
    Atomic ordering and magnetic properties in Nd57Fe20B8Co5Al10 solids (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3565-3569 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nd57Fe20B8Co5Al10 bulk cylinders and ribbons were quenched from the melt at different cooling rates using copper mold casting and melt spinning, respectively. Both the melt-spun ribbons and the cast cylinders display x-ray diffraction patterns without obvious crystalline peaks. However, the ribbons show soft magnetic properties, the cylinders are hard magnetic, and the crystallized alloys are not ferromagnetic at all. On the other hand, the cylinders show different exothermic transformation behavior than the ribbons upon heating to elevated temperatures. While the ribbons are regarded as amorphous, the structure of the cylinders prepared at slower cooling rate is considered to consist of metastable ordered clusters. This structure forms in the undercooled melt most likely due to intensive generation of ordered nuclei and slow growth kinetics. The magnetic coherence length, which is equivalent to the dimension of the ordered clusters, may be larger than the exchange length. Therefore, the cylinders shows much larger coercivity than the ribbons. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288697
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  • 2
    Electronic Resource
    Electronic Resource
    Two-phase high-performance Nd–Fe–B powders prepared by mechanical milling (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1540-1544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline two-phase NdFeB+α-Fe material was prepared by milling techniques and subsequent heat treatment. These isotropic exchange-coupled powders show excellent hard magnetic properties with enhanced remanences up to 1.20 T and energy densities (BH)max around 150 kJ/m3. The performance is based on (i) the use of grain refining additions, (ii) partial substitution of Fe by Co and (iii) the use of pre-melted master alloys. The distribution of Co among the hard and soft magnetic phases upon milling and annealing is studied via Curie temperature measurements up to 10 at. % Co substitution. The effect of Co on the intrinsic properties is estimated and clarifies the extrinsic magnetic behavior. An overview of samples prepared with different milling techniques and compositions is presented. It summarizes the above listed, three different approaches to improve the magnetic performance together with the influence of the phase ratio of hard and soft magnetic phases. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1380223
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  • 3
    Electronic Resource
    Electronic Resource
    Phase formation in mechanically alloyed Nb-Al powders (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1399-1401 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nb-Al alloys have been prepared by mechanical alloying of elemental crystalline powders and investigated with x-ray diffraction and transmission electron microscopy. Crystalline equilibrium phases form for Al-rich alloys. Amorphous phase formation is observed for the Nb50Al50 composition. Mechanically alloyed powders with more than 70 at. % Nb exhibit the metastable bcc (A2) solid solution which transforms after thermal annealing into the A15 phase. Formation of the different phases can be understood by considering the free-energy curves of the amorphous and bcc phases as calculated from the phase diagram and additional thermodynamic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99989
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of quasicrystals by mechanical alloying (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 117-119 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quasi-crystalline Al65Cu20Mn15 powder has been produced by mechanical alloying from crystalline elemental powders. The alloying process has been monitored by x-ray diffraction, and the resulting product has been characterized by transmission electron microscopy. The quasi-crystalline phase forms after about 90 h of milling. The crystallization temperature and enthalpy have been determined by differential scanning calorimetry. The results are compared with data for melt-spun material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102394
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  • 5
    Electronic Resource
    Electronic Resource
    Epitaxial growth of YBa2Cu3O7−x thin films by a laser evaporation process (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1557-1559 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of YBa2 Cu3 O7−x have been grown epitaxially in c-axis orientation on 〈100〉 SrTiO3 by pulsed excimer laser evaporation from a stoichiometric 1-2-3 target. The substrate temperature was adjusted between 720 and 780 °C, and the oxygen partial pressure during the deposition was chosen in the range 0.1–0.3 mbar. Cooled to ambient temperature in situ for 1 h in flowing oxygen gas, the films showed complete diamagnetism and zero resistance at 90 K with a transition width of 2 K. Critical current densities of 2.2×106 A/cm2 in zero magnetic field and 1.5×105 A/cm2 at 2 T were measured at 77 K. The resistivity at 100 K was about 60 μΩ cm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100437
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic hardening of Pr-Fe-Co-B alloys by rapid quenching (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 393-395 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the magnetic properties of liquid-quenched Pr15 (Fe1−x Cox )77 B8 over the whole range of Co concentrations. The coercivity Hci and the remanence Jr depend on the Co content in the same way as in Nd15 (Fe1−x Cox )77 B8 . For the ternary Pr-Co-B a high Hci , as large as 15.2 kA/cm, has been obtained. In Co-rich alloys the temperature dependence of Hci and Jr is limited by the spin reorientation at temperatures well below the Curie point. Except for Pr15 Co77 B8 , annealing of overquenched ribbons leads to substantially lower coercivities. The possible microstructural origin of the magnetic hardening is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101455
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  • 7
    Electronic Resource
    Electronic Resource
    Millimeter wave surface resistance of epitaxially grown YBa2Cu3O7−x thin films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 757-759 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the surface resistance of two c-axis oriented YBa2Cu3O7−x thin-film samples in a copper host cavity at 86.7 GHz between 4.2 and 300 K. High quality films of 0.6 and 0.4 μm thickness have been grown epitaxially on SrTiO3 by pulsed excimer laser ablation. Their millimeter wave absorption drops sharply at a transition temperature of 86 and 88 K to a corresponding surface resistance at 77 K of 18 mΩ and less than 8 mΩ, respectively. These values exceed the best results on polycrystalline samples and come close to the expectation from classical superconductors. Therefore, applications of high Tc superconductors up to THz frequencies can be envisaged now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101472
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  • 8
    Electronic Resource
    Electronic Resource
    Irradiation-induced enhancement of the critical current density of epitaxial YBa2Cu3O7−x thin films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1051-1053 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of YBa2Cu3O7−x have been prepared epitaxially on 〈100〉 SrTiO3 by laser evaporation in a single-step process. The resistivity of the films decreases linearly with temperature and is measured to 80 μΩ cm at 100 K. The samples are completely superconducting at 88 K. The critical current densities are as high as 5×106 A/cm2 at 77 K in strip lines of 8 μm width. Irradiation with 25 MeV 16O ions at 77 K combined with in situ measurements was applied to study the influence of lattice disorder on superconducting properties. The resistivity ρ increases, whereas the critical superconducting temperature Tc0 and the critical current density jc in the absence of a magnetic field decrease proportionally to the ion fluence. Contrary to this behavior, we observe an enhancement of jc in magnetic fields larger than 1 T. The maximum enhancement is about a factor of 2 at a fluence of 1014 16O/cm2. This increase is due to pinning at irradiation-induced pinning centers. Simultaneously the upper critical magnetic field Bc2 (T) exhibits an increasing positive curvature leading to a crossover with Bc2(T) of the unirradiated samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101423
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  • 9
    Electronic Resource
    Electronic Resource
    Isotropic and anisotropic Nd-Fe-B-type magnets by mechanical alloying and hot pressing (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 342-343 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mechanically alloyed Nd-Fe-B powder has been formed to compacted isotropic and anisotropic magnets by hot pressing and die upsetting. The coercivity and its composition dependence of hot-pressed samples are similar to those obtained for resin-bonded samples of the reacted powder. A ratio of up to 2.6 was obtained for the remanences measured parallel and perpendicular to the press direction during die upsetting in preliminary experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100602
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  • 10
    Electronic Resource
    Electronic Resource
    Beneficial effect of Co substitution on the magnetic properties of rapidly quenched Nd-Fe-B (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 697-699 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Isotropic Nd15(Fe1−xCox)77B8 ribbons are produced by conventional melt spinning. For moderate Co additions the coercivity HcI increases while the remanence Jr remains almost constant. Co contents above x=0.3 lead to decreasing HcI and Jr values. The beneficial effect of Co on coercivity is ascribed to the occurrence of a Nd-Fe-Co minority phase which serves as pinning center for domain walls. The temperature characteristic of the coercivity and the remanence is substantially improved due to the increased Curie temperature Tc and the pinning-type behavior of the material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98339
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