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  • Artikel  (217)
  • Forschungsdaten
  • Artikel: DFG Deutsche Nationallizenzen  (217)
  • 1
    Digitale Medien
    Digitale Medien
    Measurement of trapped flux distribution in a high-Tc superconductor using a flux-gate magnetometer : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5635-5637 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The distribution of the trapped flux was measured using a miniaturized flux-gate magnetometer with resolution as high as 0.46 mG at 77 K for a BiSrCaCuO high-Tc superconductor cooled down to 77 K in the presence of ac magnetic field (0.5–50 Hz) of 0.6 G in peak-to-peak and in-plane thermal gradient. The amplitude of the trapped flux decreased with increasing the frequency of ac magnetic field. The amplitude was as small as 2 mG for a 50 Hz ac field, and 43 mG for a 0.5 Hz ac field. The amplitude also became small when the cooling rate was made slow. A symbiotic combination of the high-Tc superconducting magnetic shield and the ferromagnetic one with magnetic shaking is proposed, in which merits of both can be enhanced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353621
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  • 2
    Digitale Medien
    Digitale Medien
    A new two-dimensional coil system compensating X,Y,Z components of leakage field from an aperture of magnetic shields (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6876-6876 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lightweight magnetic shields of high performance are required for the precise magnetic field measurements such as brain field measurement by SQUID magnetometers. Most of the present magnetic shielding rooms rely on ferromagnetic enclosures to isolate the area to be shielded from outside and, as a result, become heavy and expensive. In this paper, we propose a new method to compensate the leakage of noise field from an aperture of magnetic shields. The proposed method exploits the flux pattern just inside the aperture of the shielding body. Figure 1 depicts this method. Three flat coils mutually orthogonal and to be placed parallel inside the aperture are driven by the feedback signal to cancel each of three components detected by a three-axis fluxgate magnetometer. The important point of this method is that the coil system is flat unlike other active shielding system employing Helmholtz coils. Numerical results obtained for a superconductor vessel showed that the transverse field was attenuated by a factor of 100. Applying this method, the cylindrical shielding case of superconductor or of ferromagnet can be shortened with high shielding factor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352471
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  • 3
    Digitale Medien
    Digitale Medien
    A new method for reducing hysteresis of torque sensors: Cross magnetic shaking : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4919-4921 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Cross magnetic shaking, a new method for reducing hysteresis, is proposed for shaft torque sensors based on the magnetostrictive effect of the steel shaft. In this method, an auxiliary magnetic field (shaking field) is superposed perpendicularly to the exciting field while differences in permeabilities along lines of tension and of compression are detected by the field at the shaft surface. Hysteresis measured for a quench-hardened steel shaft of 25 mm diameter under the applied torque from −490 to 490 Nm was reduced by about nine times and sensitivity increased by a factor of 2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348200
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  • 4
    Digitale Medien
    Digitale Medien
    Low-frequency characteristic of the enhanced incremental permeability by magnetic shaking (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5583-5585 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In order to analyze the mechanism of magnetic shaking, the permeability and the energy losses for a small amplitude, low-frequency exciting field are studied under magnetic shaking in comparison with those under the normal condition (without shaking). The permeability and the energy losses were measured for a Metglas 2705M amorphous ribbon wound core by a lock-in technique in the frequency range of 1–20 Hz under both magnetic shaking (2.7 A/m, 1 kHz) and the normal condition. The effects of the magnetic shaking on the domain wall pinning, the mean wall velocity, and the number of the active walls are described. The strong frequency dependence of the enhanced incremental permeability even at low frequency is explained as a result of these effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345891
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  • 5
    Digitale Medien
    Digitale Medien
    Planar inductors with a new coil configuration (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5368-5368 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High-frequency (f≥1 MHz) magnetic power devices are key elements for developing compact and low-profile switching power supplies. Planar inductors with a flat coil are investigated,1–3 however, a problem arising from the use of a flat coil is not addressed. The problem is that normal components to the magnetic plate inevitably exist in the exciting fields from a flat coil and that those components induce severe in-plane eddy currents. The problem is most typical in the case of a spiral coil. In this paper, a new flat coil is proposed (see Fig. 1) for planar inductors which greatly improves the problem because paths of eddy currents are chopped up corresponding to the mesh size of the coil. It is obvious that density of eddy currents becomes small when the mesh size becomes fine. Sandwich planar inductors with a proposed coil (mesh coil) and a meander one were prepared for preliminary tests using pairs of Metglas 2705M amorphous ribbons of 50×50 mm2 and 100-μm copper wires, where the mesh size was 3 mm, equal to the pitch of the meander coil. Inductances at 1 MHz were 1.85 μH for the mesh coil and 2.25 μH for the meander one, whereas Qmax=5 at 6 MHz for the mesh coil and 4.5 at 2 MHz for the meander one. Advantages of the mesh coil may further become clear when it is made on the magnetic plates with thin insulating layer in between by IC or thick-film process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348033
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  • 6
    Digitale Medien
    Digitale Medien
    Foucault imaging of superconducting fluxons (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4096-4103 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Foucault method, one of the classical Lorentz microscopy techniques, is here investigated in order to demonstrate its applicability to in-focus observations of superconducting fluxons. As the deflections involved are of the order of 10−5−10−6 rad, low-angle techniques, high brightness, coherent illumination, and a low aberration magnetic stage are needed. The first experimental results are presented and discussed in relation with a theoretical model for the fluxon which allows the interpretation of the main features of the observed patterns. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.370317
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  • 7
    Digitale Medien
    Digitale Medien
    Effective shielding for low-level magnetic fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5696-5698 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An effective method of shielding slowly varying low-level magnetic fields is presented. The key of this method is the use of soft magnetic materials with a highly rectangular B-H loop and the application of the shaking field to them. Metglas 2705M amorphous ribbon of about 22 μm in thickness was used in the experiments since it has almost vertical flanks in the dc B-H loop in as-prepared state and small coercivity Hc∼0.5 A/m. A shielding factor of the cylindrical case with a copper pipe inside (diameter : 60 mm; length : 100 mm) and with two crossed layers of the ribbon outside was measured against low-level disturbing fields of 10 Hz applied transversely to the case. Although the shielding factor was as small as 3.5 without shaking, it became higher than 150 under the shaking field of 1 kHz, 2.9 A/m(rms). This value is far better than that with Mumetal or 4-79 Mo-Permalloy. A shaking frequency as high as 1 kHz or higher makes it easy to suppress the leakage of the shaking field into the shielded space.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.342278
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  • 8
    Digitale Medien
    Digitale Medien
    Localized stimulation of neural tissues in the brain by means of a paired configuration of time-varying magnetic fields (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5862-5864 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A method of localized stimulation of the human brain is proposed. The basic idea is to concentrate induced eddy currents locally in the vicinity of a target in the cortex by a pair of coils which are positioned outside the head so that time-varying magnetic fields pass through the head in the opposite directions around a target. The eddy currents induced at the target are expected to flow together, which results in an increased current flow at the target. Spatial distributions of induced eddy currents are calculated in cubical and spherical volume conductor models by a finite element method. The results show that the current vectors make themselves two vortexes which flow together at the target. The current density at the target makes a peak which is higher by 2–3 times than current densities at nontarget regions. The validity of the proposed method is demonstrated by experiments using frog nerve-muscle preparations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.342181
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  • 9
    Digitale Medien
    Digitale Medien
    Time-resolved observation of thermal oscillations by transmission electron microscopy (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 940-942 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Time-dependent acoustic oscillations driven by stochastic thermal force have been observed by means of transmission electron microscopy. An electron-beam current passing in the vicinity of the edge of the vibrating sample, and thereby modulated, was led through an aperture at the image plane and measured with the electron counting technique as the power spectral density function, allowing the resonant frequency and the Q factor to be found. This enables estimation of the Young's modulus and the internal friction. The method can be extended to the investigation of the elastic properties of nanoscaled samples. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118447
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  • 10
    Digitale Medien
    Digitale Medien
    Small angle electron diffraction and Foucault mode Lorentz microscopy of superconducting vortex lattice (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 1228-1230 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Small angle electron diffraction patterns from vortex lattices in Nb thin films were observed using a field emission transmission electron microscope. It was possible to obtain diffraction patterns in magnetic fields of up to 1000 G, from selected areas of (1–10) μm in diameter, and in (1–30) s. The degree of order of the vortex lattice was determined from the fine structure of the diffraction pattern. We also demonstrated Foucault mode Lorentz microscopy by using a diffraction technique. Vortices appeared by diffraction contrast in a focused micrograph, and therefore both vortices and material defects were simultaneously observed. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.369347
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