Physical properties, crystal and magnetic structure of layered Fe1.11Te1-xSex superconductors

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2011, Vol.82 (2), p.113-121
• Main Authors: Xiao, Y., Su, Y., Kumar, C. M. N., Ritter, C., Mittal, R., Price, S., Perßon, J., Brückel, Th
• Format: Article
• Language: English
• Subjects: Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fluid- and Aerodynamics; Magnetic properties; Metals, alloys and compounds (a15, 001c15, laves phases, chevrel phases, borocarbides, etc.); Physics; Physics and Astronomy; Properties of type I and type II superconductors; Solid State and Materials; Solid State Physics; Superconducting materials (excluding high-tc compounds); Superconductivity
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2011-10567-6

The physical and structural properties of Fe 1.11 Te and Fe 1.11 Te 0.5 Se 0.5 have been investigated by means of X-ray and neutron diffraction as well as physical property measurements. For the Fe 1.11 Te compound, the structure distortion from a tetragonal to monoclinic phase takes place at 64 K accompanied with the onset of antiferromagnetic order upon cooling. The magnetic structure of the monoclinic phase was confirmed to be of antiferromagnetic configuration with a propagation vector k = (1/2, 0, 1/2) based on Rietveld refinement of neutron powder diffraction data. The structural/magnetic transitions are also clearly visible in magnetic, electronic and thermodynamic measurements. For superconducting Fe 1.11 Te 0.5 Se 0.5 compound, the superconducting transition with T c = 13.4 K is observed in the resistivity and ac susceptibility measurements. The upper critical field H c 2 is obtained by measuring the resistivity under different magnetic fields. The Kim’s critical state model is adopted to analyze the temperature dependence of the ac susceptibility and the intergranular critical current density is calculated as a function of both field amplitude and temperature. Neutron diffraction results show that Fe 1.11 Te 0.5 Se 0.5 crystalizes in tetragonal structure at 300 K as in the parent compound Fe 1.11 Te and no structural distortion is detected upon cooling to 2 K. However an anisotropic thermal expansion anomaly is observed around 100 K.