ترغب بنشر مسار تعليمي؟ اضغط هنا

AC susceptibility in deoxygenated YBCO single crystals

324   0   0.0 ( 0 )
 نشر من قبل A. J. Moreno
 تاريخ النشر 1999
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We measured the first and third harmonic of the complex AC susceptibility in YBCO single crystals with different oxygen content. The amplitude of the AC field was varied in presence of an external DC field both applied parallel to the c axis of the crystals. We show evidence that deoxygenation leads to a reduction of bulk pinning strength and consequently to a stronger contribution of geometrical barriers.



قيم البحث

اقرأ أيضاً

The Abricosov vortex and bundles dynamics was experimentally investigated in Earths magnetic field range. Isothermal relaxation features in YBCO single crystal samples with strong pinning centers were studied for different sample-field orientation. T he normalized relaxation rate S obtained allowed to estimate the effective pinning potential U in the bulk of the YBCO sample and its temperature dependence, as well as the critical current density Jc. A comparison between the data obtained and the results for similar measurements in significantly higher magnetic fields was performed. To compare different Jc measuring techniques magnetization loop M(H) measurements, were made. These measurements provide many important parameters of the sample under study (penetration field Hp, first critical field Hc1, etc.) that contain the geometrical configuration of the samples.
The effect of annealing on the basal-plane electrical resistivity of the YBa$_2$Cu$_3$O$_{7-delta}$ single crystals is studied in a broad range of oxygen contents. Within the framework of s-d scattering of electrons by phonons, an increase in the oxy gen deficit index, $delta$, leads to a significant increase in the Debye temperature, $theta$, which is associated with the isotropization of the phonon spectrum as the concentration of oxygen vacancies increases. Near the optimal doping, the role of the paraconductivity becomes crucial, whereas its contribution decreases with increasing $delta$. At large values of $delta$ some deviations from the s-d model of electron scattering by phonons are observed at room temperature, while no paraproductivity is observed. In the superconducting transition region, a 2D-3D crossover is observed, which shifts in the direction of $T_c$ with increasing $delta$. The estimate for the transverse coherence length is about $1$,AA.
Irradiation with electrons is an efficient approach to inducing a large number of defects with a minimal impact on the material itself. Analysis of the energy transfer from an accelerated particle smashing into the crystal lattice shows that only ele ctrons with MeV energies produce point defects in the form of interstitial ions and vacancies that form perfect scattering centers. Here, we investigate the changes in the resistive characteristics of YBCO single crystals from the 1-2-3 system after several steps of low-temperature irradiation with $0.5-2.5$,MeV electrons and irradiation doses of up to $8.8times10^{18}$,cm$^{-2}$. The penetration depth of such electrons is much larger than the crystal thickness. We reveal that defects appearing in consequence of such electron irradiation not only increase the residual resistance, but they affect the phonon spectrum of the system and lower the superconducting transition temperature linearly with increase of the irradiation dose. Furthermore, the irradiation-induced defects are distributed non-uniformly, that manifests itself via a broadening of the superconducting transition. Interestingly, the excess conductivity remains almost unaffected after such electron irradiation.
121 - R. V. Vovk , G. Ya. Khadzhai , 2019
The influence of irradiation by electrons with energies of $0.5-2.5$,MeV at temperatures of about $10$,K on the basal-plane resistivity of the YBa$_2$Cu$_3$O$_{7-delta}$ single crystals is investigated in the range from $T_c$ to $300$,K. The resistiv ity temperature dependence is determined by defects arising due to the irradiation. These defects directly affect the superconducting transition, decreasing $T_c$ and increasing the transition width without significant distortions of its shape. The resulting defects also lead to an increase in the Debye temperature due to a reduction of the anisotropy, and a noticeable increase in the scattering by phonons in the sample. The excess conductivity does not change with the irradiation used.
206 - X. F. Wang , T. Wu , G. Wu 2009
Sizable single crystals of $BaFe_2As_2$ have been grown with self-flux method. The crystals are plate-like with c-axis perpendicular to the plane. The size can be as large as 3 x 5 x 0.2 $mm^3$. The resistivity anisotropy ($rho_c/rho_{ab}$) is as lar ge as about 150, and independent of temperature. The transport in ab plane and along c-axis direction shares the same scattering mechanism. In contrast to the magnetic behavior of polycrystalline samples, no Curie-Weiss behavior are observed, a temperature linear dependent susceptibility occurs above spin-density-wave (SDW) transition. The susceptibility behavior is very similar to that of antiferromagnetic SDW chromium. Magnetic behavior of single crystal definitely gives evidence for existence of local moment except for the contribution to susceptibility from itinerant electrons. A resistivity minimum strongly dependent on magnetic field is observed. A log(1/T) divergency, similar to that of the underdoped cuprates, happens at low temperature. Here we first present intrinsic transport and magnetic properties, and their anisotropy from high quality single crystal.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا