اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMagnetic Relaxation in the Peak Effect Region of CeRu$_2$
55
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The different pinning strengths of the flux line lattice in the peak effect (PE) region of a polycrystalline sample of CeRu$_2$ with a superconducting transition temperature {$T_c = 6.1$ K} have been probed by means of magnetization measurements with a SQUID magnetometer as the temperature $T$ and the magnetic field $H$ are varied. Magnetic relaxation measurements were used to monitor the flux line dynamics in the PE region. For {$T < 4.5$ K} and $H < H_P$, where $H_P$ is the field where the magnetization reaches a maximum in the PE region, the relaxation rate was found to be significantly larger in the descending-field branch of the PE than it is in other sections of the PE region. For {$T geq 4.5$ K}, the relaxation rate in the entire PE region is so large that the magnetization reached a stable (equilibrium) value within {$10^4$ s}. This experimentally determined stable state appears as an increase of the magnetization in the PE region and has a dome shape superimposed on a linear interpolation through the PE region. It was also found that the PE in CeRu$_2$ can be suppressed by rapid thermal cycling of the sample between {10 K} and {300 K} four times. The reversible magnetization after the PE has been suppressed coincides with the linear interpolation through the PE region, in contrast to the behavior of the equilibrium magnetization when the PE is present. PACS number: 74.25.Qt, 74.70.Ad
قيم البحث
اقرأ أيضاً
Nonmagnetic Zn impurities are known to strongly suppress superconductivity. We review their effects on the spin excitation spectrum in $rm YBa_2Cu_3O_{7}$, as investigated by inelastic neutron scattering measurements.
We have studied a quinary Fe-based superconductor Sr$_2$VFeAsO$_3$ by the measurements of x-ray diffraction, x-ray absorption, M{o}ssbauer spectrum, resistivity, magnetization and specific heat. This apparently undoped oxyarsenide is shown to be self
doped via electron transfer from the V$^{3+}$ ions. We observed successive magnetic transitions within the VO$_2$ layers: an antiferromagnetic transition at 150 K followed by a weak ferromagnetic transition at 55 K. The spin orderings within the VO$_2$ planes are discussed based on mixed valence of V$^{3+}$ and V$^{4+}$.
A magnetic field relaxation at the center of a pulse-magnetized single-domain Y-Ba-Cu-O superconductor at 78K has been studied. In case of a weak magnetization, the magnetic flux density increases logarithmically and normalized relaxation rate define
d as S=-d(lnB)/d(lnt) is negative (S=-0.037). When an external magnetic field magnitude increases, the relaxation rate first decreases in absolute value, then changes sign (becomes positive, S>0) and after reaching some maximum finally reduces to a very small value. Non-monotonous dependence of S vs Ha is explained by a non-homogeneous local temperature distribution during a pulse magnetization.
Longitudinal-field muon-spin-relaxation measurements have revealed inhomogeneous distribution of the internal magnetic field at temperatures above the bulk superconducting (SC) transition temperature, $T_{rm c}$, in slightly overdoped Bi$_2$Sr$_2$Ca$
_{1-x}$Y$_x$Cu$_2$O$_{8+delta}$. The distribution width of the internal magnetic field, $Delta$, evolves continuously with decreasing temperature toward $T_{rm c}$. The origin of the increase in $Delta$ is discussed in terms of the creation of SC domains in a sample.
Low temperature thermal conductivity, $kappa$, of optimally-doped Bi2212 was studied before and after the introduction of point defects by electron irradiation. The amplitude of the linear component of $kappa$ remains unchanged, confirming the univer
sal nature of heat transport by zero-energy quasiparticles. The induced decrease in the absolute value of $kappa$ at finite temperatures allows us to resolve a nonuniversal term in $kappa$ due to conduction by finite-energy quasiparticles. The magnitude of this term provides an estimate of the quasiparticle lifetime at subkelvin temperatures.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
