اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديد{mu}SR and NMR study of the superconducting Heusler compound YPd2Sn
262
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report on muon spin rotation/relaxation and $^{119}$Sn nuclear magnetic resonance (NMR) measurements to study the microscopic superconducting and magnetic properties of the Heusler compound with the highest superconducting transition temperature, ypd ($T_c=5.4$ K). Measurements in the vortex state provide the temperature dependence of the effective magnetic penetration depth $lambda(T)$ and the field dependence of the superconducting gap $Delta(0)$. The results are consistent with a very dirty s-wave BCS superconductor with a gap $Delta(0)=0.85(3)$ meV, $lambda(0)= 212(1)$ nm, and a Ginzburg-Landau coherence length $xi_{mathrm{GL}}(0)cong 23$ nm. In spite of its very dirty character, the effective density of condensed charge carriers is high compared to the normal state. The mSR data in a broad range of applied fields are well reproduced by taking into account a field-related reduction of the effective superconducting gap. Zero-field mSR measurements, sensitive to the possible presence of very small magnetic moments, do not show any indications of magnetism in this compound.
قيم البحث
اقرأ أيضاً
The superconducting ground state of newly reported ZrIrSi is probed by means of $mu$SR technique along with resistivity measurement. The occurrence of superconductivity at $T_mathrm{C}$ = 1.7 K is confirmed by resistivity measurement. ZF-$mu$SR study
revealed that below $T_mathrm{C}$, there is no spontaneous magnetic field in the superconducting state, indicates TRS is preserved in case of ZrIrSi. From TF-$mu$SR measurement, we have estimated the superfluid density as a function of temperature, which is described by an isotropic $s-$wave model with a superconducting gap $2Delta(0)/k_mathrm{B}T_mathrm{C}$ = 5.1, indicates the presence of strong spin-orbit coupling. {it Ab-initio} electronic structure calculation indicates that there are four bands passing through the Fermi level, forming four Fermi surface pockets. We find that the low-energy bands are dominated by the $4d$-orbitals of transition metal Zr, with substantially lesser weight from the $5d$-orbitals of the Ir-atoms.
We present a detailed NQR, NMR and $mu $SR study of a magnetic phase obtained during a topotactic chemical reaction of YBa$_{2}$Cu$_{3}$O$_{6.5}$ high- temperature superconductor with low-pressure water vapor. Our studies give straightforward evidenc
e that the empty Cu(1) chains play the role of an easy water insertion channel. It is shown that the NQR spectrum of the starting material transforms progressively under insertion of water, and completely disappears when one H$_{2}$O molecule is inserted per unit cell. Similarly, a Cu ZFNMR signal characteristic of this water inserted material appears and grows with increasing water content, which indicates that the products of the reaction are non-superconducting antiferromagnetic phases in which the bilayers are ordered. These antiferromagnetic phases are felt by proton NMR which reveals two sites with static internal fields of 150 and about 15 Gauss respectively. Two muon sites are also evidenced with similar local fields which vanish at $Tapprox 400$ K. This indicates that the magnetic phases have similar N{e}el temperatures as the other bilayer undoped compounds. An analysis of the internal fields on different sites of the structure suggests that they can be all assigned to a single magnetic phase at large water content in which the Cu(1) electron spins order with those of the Cu(2). It appears that even samples packed in Stycast epoxy resin heated moderately at a temperature (200$^{0}$C) undergo a reaction with epoxy decomposition products which yield the formation of the same final compound. It is then quite clear that such effects should be considered quite seriously and avoided in experiments attempting to resolve tiny effects in such materials, as those performed in some recent neutron scattering experiments.
Polycrystalline HfPd2Al has been synthesized using the arc-melting method and studied under ambient pressure conditions by x-ray diffraction from room temperature up to 450^oC. High pressure x-ray diffraction up to 23 GPa was also performed using Dia
cell-type membrane diamond anvil cells. The estimated linear thermal expansion coefficient was found to be {alpha} = 1.40(3)x10^{-5} K^{-1}, and the bulk modulus derived from the fit to the 3rd order Birch-Murnaghan EOS (BMEOS) is B0 = 97(2) GPa. Resistivity studies under applied pressure (p < 7.49 GPa) showed a linear decrease of superconducting critical temperature with increasing pressure and the slope dTc/dp = -0.13(1) K GPa^{-1}. The same behavior is observed for the electron-phonon coupling constant {lambda_{ep}}(p) that changes from 0.67 to 0.6, estimated for p = 0.05 GPa and 7.49 GPa, respectively. First principles electronic structure and phonon calculation results are presented and used to estimate the magnitude of electron-phonon interaction {lambda_{ep}} and its evolution with pressure. Theoretical results explain the experimentally observed decrease in Tc due to considerable lattice stiffening.
$^{59}$Co NMR spectra in oriented powders of Na$_{0.35}$CoO$_{2}$ and in its hydrated superconducting phase (HSC) Na$_{0.35}$CoO$_{2}$,1.3H$_{2}$O reveal a single electronic Co state with identical $T$ independent NMR shift tensor. These phases diffe
r markedly from Na$_{0.7}$CoO$_{2}$, in which we resolve 3 types of Co sites. The large T variation of their spin susceptibilities $chi ^{s}$ and the anisotropy of the orbital susceptibility $chi ^{orb}$ allow us to conclude that charge disproportionation occurs, in a non magnetic Co$^{3+}$ and two magnetic sites with about 0.3 and 0.7 holes in the $t_{2g}$ multiplet. The data are consistent with those for the single Co site in the anhydrous and HSC phase assuming the expected Co$^{3.65+}$ charge.
The results of heat capacity C_p(T, H) and electrical resistivity rho(T,H) measurements down to 0.35 K as well as muon spin relaxation and rotation (muSR) measurements on a noncentrosymmetric superconductor LaIrSi3 are presented. Powder neutron diffr
action confirmed the reported noncentrosymmetric body-centered tetragonal BaNiSn3-type structure (space group I4,mm) of LaIrSi3. The bulk superconductivity is observed below T_c = 0.72(1) K. The intrinsic Delta C_e/gamma_n T_c = 1.09(3) is significantly smaller than the BCS value of 1.43, and this reduction is accounted by the alpha-model of BCS superconductivity. The analysis of the superconducting state C_e(T) data by the single-band alpha-model indicates a moderately anisotropic order parameter with the s-wave gap Delta(0)/k_B T_c = 1.54(2) which is lower than the BCS value of 1.764. Our estimates of various normal and superconducting state parameters indicate a weakly coupled electron-phonon driven type-I s-wave superconductivity in LaIrSi3. The muSR results also confirm the conventional type-I superconductivity in LaIrSi3 with a preserved time reversal symmetry and hence a singlet pairing superconducting ground state.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
