Seminars Archive

Substitution studies on the FeySe_1-xTe_x system

Abstract
In FeySe_1-xTe_x the superconducting and magnetic properties not only depend on the Se-Te ratio x, but also strongly on the Fe content y. The superconducting and magnetic properties of the single crystals of various compositions were studied by means of x-ray diffraction, SQUID magnetometry, muon spin rotation, and elastic neutron diffraction. A series of crystals with a fixed Fe content (y = 1.03) and a fixed Se-Te ratio (x = 0.25) were grown [1,2]. The samples with the fixed y show three regimes: (i) commensurate magnetic order for x > 0.9, (ii) bulk superconductivity for x < 0.5, and (iii) a coexistence region of superconductivity with magnetism for 0.75 < x < 0.55. However, if one fixes x = 0.75, superconductivity coexisting with incommensurate magnetism occurs for the samples with y < 1. The magnetic order remains incommensurate for y > 1, but with increasing Fe content superconductivity is suppressed and the magnetic correlation length increases. These results show that the superconducting and the magnetic properties of the FeySe_1-xTe_x can be tuned not only by varying the Se/Te ratio but also by changing the Fe content. References [1] R. Khasanov, M. Bendele, A. Amato, P. Babkevich, A. T. Boothroyd, A. Cervellino, K. Conder, S. N. Gvasaliya, H. Keller, H.-H. Klauss, H. Luetkens, V. Pomjakushin, E. Pomjakushina, and B. Roessli, Phys. Rev. B 80, 140511 (2009). [2] M. Bendele, P. Babkevich, S. Katrych, S. N. Gvasaliya, E. Pomjakushina, K. Conder, B. Roessli, A. T. Boothroyd, R. Khasanov, and H. Keller, Phys. Rev. B 82, 212504 (2010).