Evidence for quasi-two-dimensional superconductivity in electron-doped Li0.48(THF)yHfNCl

Dc-magnetization and NMR measurements were carried out on a layered superconductor Li0.48(THF)yHfNCl having Tc∼26 K. For the magnetic field applied perpendicular to the basal plane (ab plane) above 10 kOe, we found a pronounced broadening of the superconducting transition in temperature dependence of magnetization and the substantial diamagnetic signals were observed as high as 2Tc, indicating the existence of superconducting fluctuations. Analysis based on the anisotropic Ginzburg-Landau model reveals that the present system is a highly anisotropic superconductor. 7Li-NMR signals were observed around zero Knight shift, indicating that the local Fermi-level density of states, N(EF), at Li site is practically nothing and the superconductivity is derived from the HfNCl layer. We have shown the unambiguous evidence for the quasi-two-dimensional superconducting character in this system

Unconventional Superconductivity in Electron-Doped Layered Li0.48(THF)yHfNCl

We report magnetic susceptibility measurements on a layered superconductor Li0.48(THF)0.3HfNCl having Tc∼26 K. The present study revealed that (a) the Fermi level density of states is small, N*(EF)∼0.25 states/(eV spin f .u.), (b) mass enhancement is negligible, γ̃∼1, (c) electron-phonon coupling is weak, λep≪1, (d) exchange enhancement is negligible, 1/(1+F0a)∼1, and (e) electronic density parameter is large, rs2D∼10.3 (i.e., low-carrier density). It is difficult to explain the origin of the high Tc in terms of the conventional phonon (BCS) mechanism of superconductivity

Thermal Decomposition of Ammonium Jarosite (NH4)Fe3(SO4)2(OH)6

Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are observed at 120, 260, 389, 510 and 541 degrees Celsius. Mass spectrometry through evolved gases confirms these steps as loss of water, dehydroxylation, loss of ammonia and loss of sulphate in two steps. Changes in the molecular structure of the ammonium jarosite were followed by infrared emission spectroscopy (IES). This technique allows the infrared spectrum at the elevated temperatures to be obtained. IES confirms the dehydroxylation to have taken place by 300 degrees Celsius and the ammonia loss by 450 degrees Celsius. Loss of the sulphate is observed by changes in band position and intensity after 500 degrees Celsius