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Dc Magnetic Field (dc + magnetic_field)
Selected AbstractsScreening Breakdown in a Plasma by Two Laser Fields and Strong DC Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005D. F. Miranda Abstract The effective static dielectric constant of an electron plasma system in the simultaneous presence of two electromagnetic waves and a strong DC magnetic field is calculated. It is found that as the difference ,, of the two electromagnetic wave frequencies matches the plasma frequency ,, a breakdown in screening occurs thereby increasing the plasma heating rate via the external fields due to inverse Bremmstrahlung. An application is made by considering the typical parameters of a hot plasma. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Measuring remanence anisotropy of hematite in red beds: anisotropy of high-field isothermal remanence magnetization (hf-AIR)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2009Dario Bilardello SUMMARY The potential of using high-field anisotropy of isothermal remanence magnetization (hf-AIR) measurements for determining the origin of natural remanent magnetization in red beds and for identifying and correcting possible red-bed inclination shallowing was investigated for specimens of the Carboniferous Shepody Formation of New Brunswick and Nova Scotia, Canada. The technique makes it possible for a typical paleomagnetic laboratory to measure the remanence anisotropy of high-coercivity hematite. High-field (hf) AIR was used in conjunction with 100 mT alternating field (af) and 120 °C thermal demagnetization to separate the contribution of hematite to the remanence anisotropy from that of magnetite/maghemite and goethite, respectively. A 5-T impulse DC magnetic field was used for the hf-AIR to reset the magnetic moment of high-coercivity hematite so that demagnetization between AIR orientations was not necessary. The ability of a 5-T field to reset the magnetization was tested by generating an isothermal remanent magnetization acquisition curve for hematite by using impulse DC magnetic fields up to 5 T in one orientation and followed by applying a field in the opposite direction at each step. Each field application was treated by 120 °C heating and 100 mT af demagnetization before measurement. At 5 T, the difference between the magnetizations applied in opposite directions disappeared indicating that no magnetic memory persisted at this field strength. We performed a validity and reproducibility test of our hf-AIR measurement technique by measuring three specimens multiple times along two orthogonal coordinate systems. The method yielded highly reproducible results and, on rotating the specimen's coordinates, the fabric rotated by 90° as expected, showing that it is not an artifact of the technique. We also measured hf-AIR on samples that had previously been chemically demagnetized in 3N HCl to remove the secondary, chemically grown pigmentary hematite. The hf-AIR fabric of leached samples is similar to that of untreated samples, but shows a better-defined magnetic lineation and imbrication. We interpret the fabric observed for the Shepody Formation to be a compactional fabric that has been reoriented by strain during folding following a flexural-slip model. [source] Magnetic anisotropy studies on FeNiCo/Ta/FeNiCo three layers film by layer sensitive ferromagnetic resonance techniquePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004F. Yildiz Abstract Two ferromagnetic layers that are separated by a non-magnetic spacer have been deposited in the presence of an external Dc magnetic field that has been applied in a mutually perpendicular direction during the deposition of each layer. This thin three-layer film of FeNiCo/Ta/FeNiCo was then studied by electron spin resonance (ESR) technique for different directions of the external magnetic field with respect to the film plane. Beside very anisotropic and strong two main modes, relatively well-resolved and very weak subsidiary peaks in ESR spectra were observed on low field side of the main modes for almost every direction of the external field. The anisotropic behavior as the field is rotated from the film normal towards to the film plane is due to strong demagnetizing field. However, two fold (axial) small anisotropies having 90 degrees phase shifts with respect to the peaks from two different layers were seen to originate from field-induced anisotropy. The small peaks are attributed to magnetostatics modes as well. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Application of ferromagnetic composite in different planar tunable microwave devicesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2001E. Salahun Abstract In this paper, several microwave devices using a ferromagnetic composite demonstrate great tunability under weak magnetizing field conditions. Indeed, a tunable bandstop of 50% tunability and phase shifters of 35°/dB figure of merit around 3 GHz and 7.8°/dB in the X -band are obtained when a 250 Oe dc magnetic field is applied. Moreover, a magnetic switch near 25 dB isolation and less than 1 dB insertion losses is realized. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 272,276, 2001. [source] Influence of Nb substituted for Fe on the microstructure and magnetic properties of Fe-based nanocomposite alloyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007N. Q. Hoa Abstract The influence of Nb substituted for Fe on the microstructure and magnetic properties including the magnetoimpedance effect of a Fe-based have been investigated. The nanocomposite structure composed of ultra-fine Fe(Si) grains embedded in an amorphous matrix was obtained by annealing the Fe-based amorphous alloy prepared by rapidly-quenched method. The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreases with increasing Nb content. The optimal heat treatment was performed at Ta = 480 °C for 30 min and showed that the ultrasoft magnetic properties of nanocomposite materials were obtained. The magnetoimpedance (MI) of these samples has been studied in range frequency from 1MHz to 5 MHz and varying a dc magnetic field within 300 Oe. The correlation between the MI effect and the soft magnetic properties is discussed. The incremental permeability ratio (PR) showed the drastic changes of soft magnetic properties as a function of annealing temperatures. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic ordering of Mn and Ru in (La0.52Ba0.48) (Mn0.51Ru0.49)O3PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007S. Y. Wu Abstract Neutron diffraction, dc magnetization, and ac magnetic susceptibility measurements have been performed to study the magnetic properties of perovskite (La0.52Ba0.48) (Mn0.51Ru0.49)O3. The compound crystallizes into a cubic Pmm symmetry with a lattice constant of a = 3.9661(4) Å at room temperature. Two anomalies, at around 160 and 60 K, can clearly be seen in the ac susceptibility results, with the peak positions for both anomalies shifting to a higher temperature as a dc magnetic field is applied. Neutron magnetic diffraction measurements show that the anomalies that occur at high and low temperatures are associated, with the ferromagnetic ordering of the Mn and the Ru spins, respectively. The ordering temperatures for the Mn and Ru spins were found to be at TC (Mn) , 195 K and TC (Ru) , 80 K, with a saturated moment of ,,z,Mn, = 2.21(5),B for the Mn spins and ,,z,Ru, = 1.00(5),B for the Ru spins. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Dependence of the permeability-frequency spectra of Fe88Zr7B4Cu alloys on dc magnetic fieldsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2004W. Qin Abstract Effects of applied dc transverse and longitudinal magnetic fields on the dynamic magnetization of Nanoperm alloys are studied by using permeability spectroscopy. It is observed that the permeability-frequency spectra of Nanoperm alloys are very sensitive to the dc transverse magnetic fields. The applied dc transverse magnetic fields may strengthen the domain wall pinning, making the permeability decrease and the relaxation frequency move toward higher frequency. The dc longitudinal magnetic fields have no significant influence on the permeability-frequency spectra. The contribution to initial permeability only results from the bulging of the domain walls parallel to the applied ac magnetic field. The effect of the Earth's magnetic field on the dynamic magnetic properties of Nanoperm alloys must be considered in actual application. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||