共查询到20条相似文献,搜索用时 34 毫秒
1.
2.
J. Sha N. L. Wang C. F. Zhu Z. H. He X. H. Chen G. E. Zhou L. Z. Cao Q. R. Zhang H. R. Yi H. C. Li 《Applied Physics A: Materials Science & Processing》1992,54(3):300-302
Nonlinear I–V characteristics of YBa2Cu3O
y
epitaxial film at different temperatures in a magnetic field of up to 5T and angles between the direction of the field and the a–b plane of 0°, 30°, 45°, 60°, and 90° were measured. We find that there are the vortex glass phase and vortex liquid phase in the mixed state. The flux creep exists in the vortex glass phase, and it obviously appears in the area around the boundary between the vortex glass phase and the vortex liquid phase. 相似文献
3.
Kazuto Hirata Ajay D. Thakur Shuuichi Ooi Takashi Mochiku 《Central European Journal of Physics》2012,10(3):576-581
Vortices (magnetic flux quanta) in the superconducting networks perforated with anti-dots (holes) arrays behave as electrons
in atomic lattice of crystals. Repulsive and attractive interaction among vortices and anti-dots resemble to those among electrons
and atoms in crystals. To confirm the variety of the vortex physics similar to the solid state physics, we have fabricated
such superconducting networks with antidots array in metallic, inter-metallic and high-T
c
superconductors (HTSCs), and have measured magneto-resistance of vortex-flow. In these materials, we have observed integer-matching
at the matching fields and fractional-matching effect between them. Most of them are well explained by commensurability between
Abrikosov vortex lattice and anti-dots array. Furthermore, the effect of the anti-dots array in HTSCs appears as another kind
of phase transitions instead of to the first-order melting transition of vortex lattice in pristine samples. 相似文献
4.
A comparative study of the thermomagnetic memory effects of J
c in two weakly pinned low T
c superconductors, Ca3Rh4Sn13 (CaRhSn) and Yb3Rh4Sn13 (YbRhSn), is presented. In both the systems, the peak effect (PE) phenomenon appears as an order-disorder transformation
through stepwise amorphization of the flux line lattice (FLL). However, in CaRhSn. we can witness another disorder-driven
transition (Bragg glass (BG) to a vortex glass (VG) in a distinct manner as in a single crystal of high T
c YBa2Cu3O7-δ for H‖c. 相似文献
5.
R. P. Dmitriev R. Z. Jagood N. K. Zhuchenko M. P. Volkov E. I. Leyarovski 《Zeitschrift für Physik B Condensed Matter》1991,83(2):155-159
The mixed state of the YBaCu2O6.9 superconducting ceramics is investigated by neutron depolarization (ND). The magnetic flux penetration into superconductor's granules can be described in terms of Bean's critical state model. The field and temperature dependence of the average angle of the vortex line deflection from the direction of the applied magnetic field are determined. In particular, this angle is zero atT/T
c
0.5 andH/H
c20.015, which is at the sameT/T
c
nearH/H
c20.017 for the metalloceramic SnMo6S8 superconductor. The latter is also studied in the present work for comparison with the YBa2Cu3O6.9 sample. TheseH/H
c2 are far below the corresponding values ofH/H
c2 for Nb, Nb–Ta. The creep of the flux line misalignments from the applied field direction is examined. 相似文献
6.
S. Sarkar A. D. Thakur C. V. Tomy G. Balakrishnan D. McK Paul S. Ramakrishnan A. K. Grover 《Pramana》2006,66(1):193-207
New experimental data are presented on the scan rate dependence of the magnetization hysteresis width ΔM(H) (∞ critical current densityJ
c(H)) in isothermalMH scans in a weakly pinned single crystal of Ca3Rh4Sn13, which displays second magnetization peak (SMP) anomaly as distinct from the peak effect (PE). We observe an interesting
modulation in the field dependence of a parameter which purports to measure the dynamical annealing of the disordered bundles
of vortices injected through the sample edges towards the destined equilibrium vortex state at a givenH. These data, in conjunction with the earlier observations made while studying the thermomagnetic history dependence inJ
c(H) in the tracing of the minor hysteresis loops, imply that the partially disordered state heals towards the more ordered state
between the peak field of the SMP anomaly and the onset field of the PE. The vortex phase diagram in the given crystal of
Ca3Rh4Sn13 has been updated in the context of the notion of the phase coexistence of the ordered and disordered regions between the
onset field of the SMP anomaly and the spinodal line located just prior to the irreversibility line. A multi-critical point
and a critical point in the (H,T) region of the Bragg glass phase have been marked in this phase diagram and the observed behavior is discussed in the light
of recent data on multi-critical point in the vortex phase diagram in a single crystal of Nb. 相似文献
7.
Results of an investigation of the path dependence of the critical current density J
c due to the plastic deformation of the flux line lattice in a weakly pinned YBa2Cu3O7-δ (YBCO) crystal for H‖c are reported. The procedure of minor hysteresis loops has been used to explore the path dependence of J
c and the metastability effects. Contrary to the behavior observed in low T
c systems. in YBCO it is found that at low temperatures, the multivaluedness in J
c(H) could persist beyond the notional peak field H
p, at which the anomalous variation in J
c(H) reaches its maximum value. 相似文献
8.
J. Yuan H.B. Wang I. Iguchi S. Arisawa A. Ishii T. Hatano 《Physica C: Superconductivity and its Applications》2009,469(15-20):1140-1142
We measured the in-plane magnetoresistance of Pr0.9LaCe0.1CuO4 (PLCCO) epitaxial thin films under various magnetic fields H applied parallel to the tetragonal c-axis. The measurements were performed at the superconducting state as well as the normal state. As the magnetic field is between the low critical field Hc1 and upper critical field Hc2, a critical scaling behavior of electrical resistivity is found. We analyze the electrical transport properties and show the magnetic field H dependence of glass transition temperature Tg and the characteristic temperature T* for the PLCCO film, which may shed some light on vortex behavior in electron-doped superconductors. 相似文献
9.
S. Kuroiwa Y. Sugiyama H. Kawano-Furukawa 《Journal of Physics and Chemistry of Solids》2007,68(11):2129-2132
The small angle neutron scattering diffraction patterns from the flux line lattice state in the layered hexagonal superconductor CaAlSi are observed. Under an applied magnetic field (H) parallel to the crystalline c-axis, a hexagonal vortex structure is observed over the entire temperature/field regions. On the other hand, the vortex configuration under H∥a shows an ellipsoidal arrangement of the first-order Bragg peaks due to the anisotropic penetration depth. It was inferred from these results that the vortex state characterized by penetration depth and coherence length in CaAlSi may be described by that of anisotropic uniaxial superconductor using London theory. 相似文献
10.
New results on the properties of niobium and vanadium in the mixed state obtained by the neutron depolarization method are presented. Magnetization measurements were taken on several samples differing in their degree of hysteresis to obtain the characteristic fieldsH c1,H + andH c2 (H + denotes the field where the major hysteresis loop for one sense joins the initial magnetization curve). The depolarization is always observed to begin atH c1 and to disappear atH +. A theoretical reexamination of the critical state concept for low-κ type-II superconductors leads to the conclusion that the maximum depolarization indicates the entrance of the entire sample into the critical state. The actual value of the depolarization is shown to be a measure of the flux line lattice distortions. Furthermore, evidence for an anisotropic flux density distribution in the mixed state is presented. 相似文献
11.
D. Ahmad I. Park G.C. Kim J.H. Lee Z.-A. Ren Y.C. Kim 《Physica C: Superconductivity and its Applications》2009,469(15-20):1052-1054
The irreversibility line and flux pinning properties of high-Tc superconductor SmFeAsO0.85 were studied using DC magnetization data. Polycrystalline SmFeAsO0.85 was prepared in a high pressure synthesis apparatus under the pressure of 6 GPa. The results of DC susceptibility showed the superconducting transition at about 55 K. A critical current density Jc(B) was calculated using Bean’s critical state model. At low temperatures (20 K), Jc(B) showed a relatively high value with weak dependence on an applied magnetic field. At higher temperatures, a stronger dependence of the magnetic field was observed, which resulted from decrease in a critical current density probably due to the flux creep effect. The irreversibility line (IL) agreed well with the flux creep theory of Matsushita et al. A comparison of normalized pinning force density with the theoretical models showed that the irreversible behavior in SmFeAsO0.85 is dominated mainly by normal point pinning (δTc) and surface pinning mechanisms. 相似文献
12.
The lattice models of thermally disordered flux line system are studied by the random walk method. We formulate rigorously the 2D model having an exact solution. In three dimensions the method leads to the generalized Bethe approximation. The critical behavior of both thermodynamic and correlation functions nearH
c1
is considered. An examination of a possible transition between entangled and disentangled phases is done. 相似文献
13.
R.B.G. Kramer A.V. SilhanekJ. Van de Vondel B. RaesV.V. Moshchalkov 《Physica C: Superconductivity and its Applications》2010,470(19):758-761
Using scanning Hall probe microscopy a direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained. We demonstrate that stable vortex configurations can be found for fields H ∼ 0.8H1, H1 and 1.6H1, where H1 corresponds to one flux quantum per pinning site. The vortex pattern at 0.8H1 corresponds to one vacancy in one of the vertices of the thin tiles whereas at 1.6H1 the vortex structure can be associated with one interstitial vortex inside each thick tile. Strikingly, for H = 1.6H1 interstitial and pinned vortices arrange themselves in ring-like structures (“vortex corrals”) which favor the formation of a giant vortex state at their center. 相似文献
14.
We present torque magnetization measurements on the quasi-2D heavy fermion superconductor CeCoIn5 at temperatures down to 20 mK and magnetic fields up to 18?T. At orientations with the magnetic field perpendicular to the conducting planes, a prominent vortex lattice peak effect is present at around 0.5H c2. The peak effect gradually disappears upon rotating the field into the plane parallel orientation. We interpret the absence of the peak effect for the plane parallel case as a transformation of the Abrikosov lattice into a Josephson vortex state, favored by the Pauli paramagnetic limit in CeCoIn5 together with the unusually large condensation energy. Additionally, we do not observe flux avalanches as found in organic superconductors and suggest that the complete absence of vortex activity in the plane parallel field orientation is crucial for the formation of Fulde–Ferrell–Larkin–Ovchinnikov superconductivity in CeCoIn5. 相似文献
15.
V. N. Zavaritskii 《JETP Letters》1997,65(8):663-669
The field H*(T) for the onset of dissipation is estimated self-consistently from the results of an investigation of the transverse resistance
and current-voltage characteristics of a Bi2Sr2CaCu2O8 (BSCCO-2212) single crystal in a mixed state. It is established that H* is close to H
c1 in the interval T
c/2⩽T⩽T
c. Rapid growth of H*(T), accompanied by a transformation of the current-voltage characteristics, as the temperature decreases below ≈ 40 K attests
to the formation of a nonvanishing region of stability of an ordered state of the vortex system, possibly as a result of a
change in the effective dimensionality of the fluxoid.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 629–634 (25 April 1997) 相似文献
16.
Z. H. Wang K. B. Li J. Fang J. L. Chen X. W. Cao 《Zeitschrift für Physik B Condensed Matter》1997,104(3):445-449
We have measured the resistivity of epitaxial YBa2Cu3O7?δ thin film as a function of temperature, current density and the magnetic field up to 8 T. The current density dependence of the effective activation energy exhibits a slight increase in the low current density range below 103 A/cm2 and a logarithmic decline in higher current density with increasing current density. The magnetic field dependence of the effective activation energy showed a crossover of vortex state from a quasi-2D for H//ab-plane to a 3D line liquid state for H//c-axis. The possible dissipation mechanisms responsible for the ln H dependence of the effective activation energy were discussed. 相似文献
17.
T. Krzysztoń K. Rogacki 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):181-187
The influence of antiferromagnetic order on the mixed state of a superconductor may result in creation of spin-flop domains
along vortices. This may happen when an external magnetic field is strong enough to flip over magnetic moments in the vortex
core from their ground state configuration. The formation of domain structure causes modification of the surface energy barrier,
and creation of the new state in which magnetic flux density is independent of the applied field. The modified surface energy
barrier has been calculated for parameters of the antiferromagnetic superconductor DyMo6S8. The prediction of two-step flux penetration process has been verified by precise magnetization measurements performed on
the single crystal of DyMo6S8 at milikelvin temperatures. A characteristic plateau on the virgin curve B(H
0) has been found and attributed to the modified surface energy barrier. The end of the plateau determines the critical field,
which we call the second critical field for flux penetration.
Received 16 August 2002 / Received in final form 22 October 2002 Published online 29 November 2002 相似文献
18.
19.
The electronic spectrum of multivortex configurations in type-II superconductors is studied taking into account the effect
of quasiparticle tunneling between the vortex cores. The tunneling is responsible for the formation of strongly coupled quasiparticle
states for intervortex distances a < a
cc
, where the critical distance a
c is of the order of several coherence lengths ξ. When analyzing the resulting spectra of vortex clusters bonded by quasiparticle
tunneling, we find a transition from a set of degenerate Caroli-de Gennes-Matricon branches to anomalous branches similar
to the ones in multiquantum giant vortices. This spectrum transformation results in the oscillatory behavior of the density
of states at the Fermi level as a function of a and could be observed in mesoscopic superconductors and disordered flux line arrays in bulk systems.
The text was submitted by the authors in English. 相似文献
20.
G. P. Mikitik 《Journal of Experimental and Theoretical Physics》2014,119(3):493-502
The lower critical field H c1 in layered superconductors is calculated under the assumption that vortex pinning by point defects is strong in these materials. We consider the case of a purely electromagnetic coupling of vortex pancakes and the case of both the electromagnetic and Josephson couplings of the pancakes in a vortex line. In the latter case, singularities in the temperature dependence of H c1 are predicted at certain characteristic temperatures. 相似文献