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  • 1
    Digitale Medien
    Digitale Medien
    The origin of hard magnetic properties in rapidly quenched Nd4Fe77.5B18.5 alloy : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6980-6982 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Until now, the origin of hard magnetic properties of rapidly quenched Nd-Fe-B alloys with lower Nd concentration is not clear. In this paper, the phase compositions of rapidly quenched Nd4Fe77.5B18.5 alloys annealed under different conditions have been studied by using zero-field spin-echo nuclear magnetic resonance (NMR) and Mössbauer effect (ME) techniques. It is found that there exists a certain amount of Nd2Fe14B phase in the samples annealed at 960 °C and ingot alloy, which have poor hard magnetic properties; while, the sample annealed under optimal condition consists only of bct-Fe3B as the main phase and a small amount of a-Fe. However, the ME result indicates that about 5 at. % Fe atoms in FeIII (8 g) site of bct-Fe3B have been replaced by Nd atoms; the NMR result demonstrates that 11B NMR spectrum is the characteristic peak of bct-Fe3B, but it broadens asymmetrically to the high frequency side, which is due to the bct-Fe3B influenced by Nd atoms. The amplitude of radio frequency (rf) excitation field required to get the maximum 11B spin-echo signal from bct-Fe3B in the sample annealed at 839 °C is only about one third as much as that required to excite the 11B in the bct-Fe3B influenced by Nd atoms in the sample annealed at 670 °C for a short time, which implies the latter has a larger coercivity field than the former. It is concluded that the origin of hard magnetic properties of Nd4Fe77.5B18.5 alloy is not related to the 2:14:1 phase, but to the change of bct-Fe3B itself.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352404
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  • 2
    Digitale Medien
    Digitale Medien
    Spin-state transition in La1−xSmxCoO3 perovskites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1331-1335 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Structural and magnetic properties of La1−xSmxCoO3 with x=0, 0.02, 0.04, 0.06, 0.08, 0.12, 0.16, and 0.2 have been systematically studied. LaCoO3 exhibits a rhombohedral structure of R3¯C symmetry. The lattice parameters decrease progressively with the incorporation of Sm, and a second orthorhombic phase of Pbnm symmetry appears for x≥0.12. The volume fraction of the orthorhombic phase is a sensitive function of the Sm content in the compounds, and increases from 16% for x=0.12 to 75% for x=0.2. Accordingly, the low-spin-to-high-spin transition of the trivalent Co ions, characterized by a steep rise of the magnetization, shifts to higher temperatures. A molecular field analysis indicates an increased energy gap, from 317 K for x=0 to 500 K for x=0.2, between the low-spin and the high-spin state, implying a stabilization of the low-spin trivalent Co ions by the presence of Sm. The enhanced compressive chemical pressure due to the introduction of Sm is suggested to be responsible for the present observations. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1336521
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  • 3
    Digitale Medien
    Digitale Medien
    Gettering of copper by bulk stacking faults and punched-out dislocations in Czochralski-grown silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4540-4546 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The characteristics of Cu precipitation on various types of defects associated with oxygen precipitation in Czochralski-grown silicon are investigated by transmission electron microscopy and the electron-beam-induced-current technique. Specimens containing dominantly either punched-out dislocations or bulk stacking faults were intentionally contaminated with Cu at various temperatures and cooled at three different rates. Colonies of Cu precipitates developed irrespective of cooling rate, apparently originating from punched-out dislocations developed around oxygen precipitates. In heavily contaminated specimens cooled fast from the contamination temperature, Cu also precipitates on Frank partial dislocations bounding stacking faults. During slow cooling, precipitation of Cu takes place on Frank partials only in lightly contaminated specimens but never in heavily contaminated specimens. Cu precipitates in colonies are thermally more stable than those formed on Frank partials. It is concluded that punched-out dislocations are more favorable precipitation sites for Cu than Frank partials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357285
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  • 4
    Digitale Medien
    Digitale Medien
    Magnetic properties of Fe/Pd multilayers grown by electron-beam evaporation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3965-3970 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetic properties of [Fe(20 A(ring))/Pd(x A(ring))]25 multilayers prepared by ultrahigh vacuum electron-beam evaporation are presented. It is found that the crystal structure of Fe layers change from bcc to fcc when the thickness of Pd layers dPd≥36 A(ring). The saturation magnetization per unit Fe volume at 5 K is enhanced and oscillates with the increment of the thickness of Pd layers, due to the polarization of Pd atoms. The magnetic hysteresis loops of samples indicate low coercive forces, and ferromagnetic coupling between the Fe layers for all Pd thicknesses (6–60 A(ring)). The conversion electron Mössbauer spectra measurements proved that the magnetic moment of fcc Fe is the same as that of the bcc Fe. It is also found that the magnetic anisotropy dependence on dPd is similar to that of the saturation magnetization, and relates to the Fe layer structure transition. The Curie temperature of Fe/Pd multilayers decreases monotonously with the increasing of dPd. The low temperature magnetization measurement of Fe/Pd multilayers suggests that the interlayer coupling between Fe layers and polarization of Pd layers influences the temperature dependence of saturation magnetization. No evidence of antiferromagnetic coupling between Fe layers and giant magnetoresistance effect is found. The relationship among structure, polarization of Pd layers, and magnetic coupling is discussed. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358579
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  • 5
    Digitale Medien
    Digitale Medien
    Granular magnetoresistance ribbon material suitable for isotropic magnetic field transducers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4918-4920 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetic granular CoCu alloy ribbons were prepared by the melt-spun method, and the structural, magnetotransport, magnetic properties, and the effects of annealing on these properties were studied by x-ray diffraction, vibrating sample magnetometer, and magnetoresistance (MR) measurements at room temperature. Giant magnetoresistance was observed over a broad range of Co concentrations with a maximum MR ratio of 7.8% (at x=0.20 and 500 °C annealing) under a magnetic field of 20 kOe at room temperature. It is found that the relationship between MR and magnetic field H depended strongly on the annealing temperature and a linear MR-H relation could be obtained at an optimum annealing condition. The MR ratio did not depend on the direction between H and electric current I. These features are very suitable for making isotropic magnetic field transducers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358442
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  • 6
    Digitale Medien
    Digitale Medien
    Acid Hydrolysis of .kappa.-Carrageenan in a Batch Reactor: Stochastic Simulation of Change of Molecular Weight Distribution with Time (1994)
    s.l. : American Chemical Society
    Biotechnology progress 10 (1994), S. 389-397 
    Details
    ISSN: 1520-6033
    Quelle: ACS Legacy Archives
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/bp00028a008
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  • 7
    Digitale Medien
    Digitale Medien
    Gettering of Fe impurities by bulk stacking faults in Czochralski-grown silicon (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1876-1878 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Gettering of Fe impurities by bulk stacking faults in Czochralski-grown silicon are investigated by means of the electron-beam-induced-current technique and transmission electron microscopy. It is found that Fe impurities only precipitate on Frank partial dislocations bounding stacking faults when the specimen is cooled slowly; however, both Frank partials and fault planes are decorated by Fe impurities when the specimen is cooled rapidly. It is explained that small oxygen precipitates on fault planes serve as the gettering centers for Fe impurities in the fast cooled specimen. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118718
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  • 8
    Digitale Medien
    Digitale Medien
    Precipitation behaviors of Cu and Fe on Frank-type partial dislocations in Czochralski-grown silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 214-216 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Precipitation behaviors of Cu and Fe on Frank-type partial dislocations bounding bulk stacking faults in Czochralski-grown silicon are investigated by means of the electron beam-induced-current (EBIC) technique and transmission electron microscopy (TEM). Frank partials in a Cu-contaminated specimen do not exhibit an EBIC contrast at room temperature when the specimen is cooled slowly; however, in the Fe-contaminated specimen, they exhibit EBIC contrast at room temperature due to their Fe contamination. The TEM micrograph shows that Cu develops precipitate colonies in the region away from stacking faults and does not precipitate on Frank partials in the specimen. The results indicate that Fe impurity decorates Frank partials more easily than Cu impurity in Si. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116464
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  • 9
    Digitale Medien
    Digitale Medien
    Temperature dependence of exchange field in exchange-spring magnets (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 8351-8353 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Pr8Fe88B4 ribbons prepared by melt spinning have been investigated by x-ray diffraction, differential thermal analysis, thermomagnetic analysis, atom force microscopy, and superconducting quantum interface device magnetometer. The results show that the annealed ribbons consist of the Pr2Fe14B and α-Fe phases. The magnetization of soft α-Fe phase remains parallel to the magnetization of the hard Pr2Fe14B phase for fields less than the exchange field (Hex). The exchange field in exchange-spring magnets, determined from the demagnetization curves measured at various temperatures, increases with decreasing grain size and measure temperature. The temperature dependence of exchange field was analyzed qualitatively by the expression Hex=(AK)1/2/(Mst). © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1368159
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  • 10
    Digitale Medien
    Digitale Medien
    Magnetic properties and giant magnetoimpedance of nanocrystalline Fe92−xZr7BxCu1 ribbons (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3873-3877 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of substitution of B for Fe on the microstructure, magnetic properties, and giant magnetoimpedance (GMI) effect has been studied for the nanocrystalline soft magnetic ribbons Fe92−2Zr7BxCu1 (x=2,4,6,8,10) annealed at 873 K for 20 min. The experimental results show that the thermal stability of the amorphous precursor is enhanced and the body-centered-cubic phase grains become smaller with increasing B content. The coercive force Hc exhibits a minimum of 2.51 A/m for the ribbon with x=8, where the effective permeability reaches the maximum. The frequency and field dependence of GMI effect is very sensitive to B content. For the ribbon with x=8, The maximal GMI ratio (ΔZ/Z)ΔZ/Z=[Z(H)−Z(Hmax)]/Z(Hmax) is about 260% at f=6.5 MHz, and the maximal sensitivity reaches value up to about 0.88% (A/m)−1 (66.6% Oe−1) at f=10.5 MHz. The correlation between the magnetic properties and the GMI effect shows that the excellent soft magnetic properties and proper transverse anisotropy play a decisive role in the occurrence of the GMI effect. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371301
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