Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInhomogeneity of the intrinsic magnetic field in superconducting YBa2Cu3OX compounds as revealed by rare-earth EPR-probe
61
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
X-band electron paramagnetic resonance on doped Er3+ and Yb3+ ions in Y0.99(Yb,Er)0.01Ba2Cu3OX compounds with different oxygen contents in the wide temperature range (4-120)K have been made. In the superconducting species, the strong dependencies of the linewidth and resonance line position from the sweep direction of the applied magnetic field are revealed at the temperatures significantly below TC. The possible origins of the observed hysteresis are analyzed. Applicability of the presented EPR approach to extract information about the dynamics of the flux-line lattice and critical state parameters (critical current density, magnetic penetration depth, and characteristic spatial scale of the inhomogeneity) is discussed
rate research
Read More
We investigate the low temperature X-band electron paramagnetic resonance (EPR) of YBa2Cu3O6 compounds with x = 6.0 doped with Dy3+, Tb3+, and Nd3+. The EPR spectra of Dy3+ and Tb3+ have been identified. The EPR of Tb3+ is used also to study the effect of suppression of high Tc superconductivity. The EPR of Nd3+ is probably masked by the intense resonance of Cu2+. All experimental EPR results compare well with theoretical estimations.
We present a ^{115}In NMR study of the quasi two-dimensional heavy-fermion superconductor CeCoIn_5 believed to host a Fulde-Ferrel-Larkin-Ovchinnkov (FFLO) state. In the vicinity of the upper critical field and with a magnetic field applied parallel to the ab-plane, the NMR spectrum exhibits a dramatic change below T*(H) which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. We argue that our results provide the first microscopic evidence for the occurrence of a spatially modulated superconducting order parameter expected in a FFLO state. The NMR spectrum also implies an anomalous electronic structure of vortex cores.
We report measurements of the pressure dependence of the superconducting transition temperature T_c in single crystal samples of the rare-earth doped superconductor Ca$_{0.73}$La$_{0.27}$Fe$_2$As$_2$. We track T_c with two techniques, via in-plane resistivity measurements and with a resonant tunnel diode oscillator circuit which is sensitive to the skin depth. We show that initially T_c rises steeply with pressure, forming a superconducting dome with a maximum T_c of ~44 K at 20 kbar. We discuss this observation in the context of other electron-doped iron pnictide superconductors, and conclude that the application of pressure offers an independent way to tune T_c in this system.
We have performed the $^{125}$Te-nuclear magnetic resonance (NMR) measurement in the field along the $b$ axis on the newly discovered superconductor UTe$_2$, which is a candidate of a spin-triplet superconductor. The nuclear spin-lattice relaxation rate divided by temperature $1/T_1T$ abruptly decreases below a superconducting (SC) transition temperature $T_c$ without showing a coherence peak, indicative of UTe$_2$ being an unconventional superconductor. It was found that the temperature dependence of $1/T_1T$ in the SC state cannot be understood by a single SC gap behavior but can be explained by a two SC gap model. The Knight shift, proportional to the spin susceptibility, decreases below $T_c$, but the magnitude of the decrease is much smaller than the decrease expected in the spin-singlet pairing. Rather, the small Knight-shift decrease as well as the absence of the Pauli-depairing effect can be interpreted by the spin triplet scenario.
Superconductivity induced by a magnetic field near metamagnetism is a striking manifestation of magnetically-mediated superconducting pairing. After being observed in itinerant ferromagnets, this phenomenon was recently reported in the orthorhombic paramagnet UTe$_2$. Under a magnetic field applied along the hard magnetization axis b, superconductivity is reinforced on approaching metamagnetism at $mu_0H_m$ = 35 T, but it abruptly disappears beyond $H_m$. On the contrary, field-induced superconductivity was reported beyond $mu_0H_m$ = 40-50 T in a magnetic field tilted by $simeq25-30deg$ from b in the (b,c) plane. Here we explore the phase diagram of UTe2 under these two magnetic-field directions. Zero-resistance measurements permit to confirm unambiguously that superconductivity is established beyond Hm in the tilted-field direction. While superconductivity is locked exactly at fields either smaller (for a H || b), or larger (for H tilted by $simeq27deg$ from b to c), than Hm, the variations of the Fermi-liquid coefficient in the electrical resistivity and of the residual resistivity are surprisingly similar for the two field directions. The resemblance of the normal states for the two field directions puts constraints for theoretical models of superconductivity and implies that some subtle ingredients must be in play.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
