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Vestgården JI Shantsev DV Olsen AA Galperin YM Yurchenko VV Goa PE Johansen TH 《Physical review letters》2007,98(11):117002
A theoretical model for how Bloch walls occurring in in-plane magnetized ferrite garnet films can serve as efficient magnetic micromanipulators is presented. As an example, the walls' interaction with Abrikosov vortices in a superconductor in close contact with a garnet film is analyzed within the London approximation. The model explains how vortices are attracted to such walls, and excellent quantitative agreement is obtained for the resulting peaked flux profile determined experimentally in NbSe(2) using high-resolution magneto-optical imaging of vortices. In particular, this model, when generalized to include charged magnetic walls, explains the counterintuitive attraction observed between vortices and a Bloch wall of opposite polarity. 相似文献
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Albrecht J Matveev AT Strempfer J Habermeier HU Shantsev DV Galperin YM Johansen TH 《Physical review letters》2007,98(11):117001
Anisotropic penetration of magnetic flux in MgB(2) films grown on vicinal sapphire substrates is investigated using magneto-optical imaging. Regular penetration above 10 K proceeds more easily along the substrate surface steps, the anisotropy of the critical current being 6%. At lower temperatures the penetration occurs via abrupt dendritic avalanches that preferentially propagate perpendicular to the surface steps. This inverse anisotropy in the penetration pattern becomes dramatic very close to 10 K where all flux avalanches propagate in the strongest pinning direction. The observed behavior is fully explained using a thermomagnetic model of the dendritic instability. 相似文献
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L. Seetha Lakshmi V Sridharan DV Natarajan V Sankara Sastry T S Radhakrishnan 《Pramana》2002,58(5-6):1019-1026
Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and
Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the
oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures
(T
p(ρ) and T
C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising
due to difference in the ionic radii between the substituent (r
M) and the Mn3+ ion (r
Mn
3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and
that of the neighboring Mn ion. 相似文献
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M. E. Gaevskii D. V. Shantsev A. V. Bobyl’ Yu. M. Gal’perin T. H. Johansen H. Hauglin 《Physics of the Solid State》1999,41(6):877-880
The paper provides the first demonstration of the efficiency of applying the magneto-optic method to studies of the spatial
and temporal magnetic-field relaxation in an YBa2Cu3O7 film strip after the transport current is switched on. It is shown that the evolution of magnetic flux distribution is adequately
described in terms of a modified Bean model with time-dependent critical current. At a time 50 ms after the current is switched
on, the critical current of the samples studied decreases by ≈15%. This proves the significance of thermally activated magnetic
flux motion (creep) in the regime investigated. The magnetic vortex pinning energy has been estimated as U
0≈20 kT.
Fiz. Tverd. Tela (St. Petersburg) 41, 965–968 (June 1999) 相似文献
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Richard DV. Espiritu Alberto V. AmorsoloJr. 《Journal of Thermal Analysis and Calorimetry》2012,107(2):483-487
Cu–Zn–Sn shape memory alloy strips with composition range of 13.70–46.30 mass% Sn were fabricated by electrodepositing Sn
on a shim brass surface and then subsequently annealed at a constant temperature of 400 °C for 120 min under flowing nitrogen.
Subjecting the Sn-plated strips to differential scanning calorimetry (DSC) analysis revealed that the austenitic start (A
s) temperature was essentially constant at 225 °C while the martensite start (M
s) temperature was consistently within the 221.5–222 °C interval. Austenite to martensite phase transformation showed two distinct
peaks on the DSC thermogram which can be attributed to the non-homogeneity of the bulk Cu–Zn–Sn ternary alloy. The latent
heats of cooling and heating were found to increase with the mass% Sn plated on the shim brass. Effect of annealing temperature
was also investigated wherein strips with an essentially constant composition of 26 mass% Sn were annealed at a temperature
range of 350–420 °C for 120 min under flowing nitrogen. Varying the annealing temperature has no significant effect on the
transformation temperatures of the ternary alloy. 相似文献
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Existing methods of measuring uhf properties of ferromagnetic substances in a resonator (and in lumped resonance systems) become inapplicable even for small samples as the Q of the electromagnetic system is increased. By regarding the magnetization oscillations in the specimen as an oscillatory system with two degrees of freedom, the possibility of measuring ferromagnetic resonance parameters in high-Q electromagnetic systems is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 87–91, August, 1971. 相似文献
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Experimental observations of time-delay-induced amplitude death in two coupled nonlinear electronic circuits that are individually capable of exhibiting limit-cycle oscillations are described. The existence of multiply connected death islands in the parameter space of coupling strength and time delay for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds [Phys. Rev. Lett. 80, 5109 (1998); Physica (Amsterdam) 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay, and the onset of both in-phase and antiphase collective oscillations. 相似文献