We present a detailed study of 75As Knight shift and spin-lattice relaxation rate 1/T1 in the normal state of stoichiometric polycrystalline LiFeAs, one of the six members of newly discovered family of iron-based superconductors. Our analysis of the Korringa relation suggests that LiFeAs exhibits moderate to strong antiferromagnetic fluctuations.
COBISS.SI-ID: 23578919
We demonstrate with the 75As nuclear magnetic resonance (NMR) measurements a coupling between isolating NdO layers and conducting FeAs layers. We discuss a role of rare-earth element on magnetism and superconductivity of REFeAsO superconductors, when the rare-earth element is magnetic. This work represents one of the first studies of newly discovered iron-based high-temperature superconductors by NMR.
COBISS.SI-ID: 22492199
In this work we isolated the face-centered cubic (fcc) and body-centered cubic (bcc) polymorphs of Cs3C60 to show how the spatial arrangement of C60 units controls the competing superconducting and magnetic electronic ground states. The magnetic ordering occurs at an order of magnitude lower temperature in the geometrically frustrated fcc polymorph (TN = 2.2 K) than in the bcc packing (TN = 46 K). Under applied hydrostatic pressure the different lattice packing of C60 units changes the superconducting transition temperature TC from 38 K in bcc to 35 K in fcc Cs3C60. The existence of two superconducting packings of the same electronically active unit reveals that Tc scales universally in a structure independent dome-like relationship with proximity to the Mott metal-insulator transition, which is governed by the role of electron correlations characteristic of high-temperature superconductors.
COBISS.SI-ID: 23639591
We report X-band electron paramagnetic resonance and 125Te and 77Se NMR measurements on single-crystalline superconducting FeSe0.42Te0.58 with Tc=11.5 K. The data provide indications for the coexistence of intrinsic localized and itinerant electronic states.
COBISS.SI-ID: 24079399
We studied the family of high-temperature iron-based superconductors NaxFeAs characterized by different sodium content. We found out that under 45 K all members of the family undergo a transition into the spin-density wave magnetic ordered state, where the portion of the Fermi surface remains gapless. This portion is directly related to the superconducting fraction as deduced from bulk susceptibility under 12 K. Our findings are consistent with the theories of coexisting magnetic order and superconductivity.
COBISS.SI-ID: 24952103