A one-dimensional charge-density wave (CDW) instability is shown to be responsible for the formation of the incommensurate modulation of the atomic lattice in the high-pressure phase of sulfur. The coexistence of, and competition between, the CDW and the superconducting state leads to the previously observed increase of T{c} up to 17 K, which we attribute to the suppression of the CDW instability, the same phenomenology found in doped layered dichalcogenides.
We report on structural, magnetic and transport properties of a new set of the high-pressuresynthesized compounds Mn1−xRhxGe (0 ≤ x ≤ 1) with the chiral magnetic ordering. The magnetic and transport properties depend substantially on the concentration of rhodium (x) and the pressure. The saturation magnetic moment corresponds to a known high-spin value for pristine MnGe (x = 0) and decreases almost linearly with increasing concentration x. In addition, XMCD spectra taken at 10 K and 2 T indicate magnetic polarization of the Rh 4d electron states and Ge 4p states, which decreases with x, too. In rhodium rich compounds (x ≥ 0.5) the temperature of the magnetic ordering increases significantly with pressure, whereas in manganese rich compounds (x < 0.5) the temperature decreases. Three different tendencies are also found for several structural and transport properties. In the intermediate range (0.3 ≤ x ≤ 0.7) samples are semiconducting in the paramagnetic phase, but become metallic in the magnetically ordered state. We carried out ab initio density-functional calculations of Mn1−xRhxGe at various concentrations x and traced the evolution of electronic and magnetic properties. The calculation results are in good agreement with the measured magnetic moments and qualitatively explain the observed trends in transport properties.
We report the high-pressure synthesis of novel superconductor MgB 2 and some related compounds. The superconducting transition temperature of our samples of MgB 2 is found to be 36.6 K. The MgB 2 lattice parameters determined via X-ray diffraction are in excellent agreement with results of our ab initio calculations. The TDPAC measurements of 111 Cd quadrupole frequency ν Q demonstrate a small increase in ν Q with decreasing temperature from T room to T He .The electric field gradient V zz at the B site calculated from first principles is in fair agreement with V zz obtained from 11 B NMR spectra of MgB 2 reported in the literature. It is also very close to V zz found in our 111 Cd TDPAC experiments, which suggests that the 111 Cd probe substitutes for boron in the MgB 2 lattice.
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