Magnetic excitations of Fe1 + ySexTe1 - X in magnetic and superconductive phases

Department of Physics, Clarendon Laboratory, Oxford University, Oxford OX1 3PU, UK.
Journal of Physics Condensed Matter (Impact Factor: 2.35). 04/2010; 22(14):142202. DOI: 10.1088/0953-8984/22/14/142202
Source: PubMed


We have used inelastic neutron scattering and muon-spin rotation to compare the low energy magnetic excitations in single crystals of superconducting Fe(1.01)Se(0.50)Te(0.50) and non-superconducting Fe(1.10)Se(0.25)Te(0.75). We confirm the existence of a spin resonance in the superconducting phase of Fe(1.01)Se(0.50)Te(0.50), at an energy of 7 meV and a wavevector of (1/2, 1/2, 0). The non-superconducting sample exhibits two incommensurate magnetic excitations at (1/2, 1/2, 0) ± (0.18, - 0.18, 0) which rise steeply in energy, but no resonance is observed at low energies. A strongly dispersive low energy magnetic excitation is also observed in Fe(1.10)Se(0.25)Te(0.75) close to the commensurate antiferromagnetic ordering wavevector (1/2 - δ, 0, 1/2), where δ≈0.03. The magnetic correlations in both samples are found to be quasi-two-dimensional in character and persist well above the magnetic (Fe(1.10)Se(0.25)Te(0.75)) and superconducting (Fe(1.01)Se(0.50)Te(0.50)) transition temperatures.

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Available from: Ekaterina Pomjakushina, Jul 10, 2014
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    • "Data in (b) was measured for k < 0 and then symmetrized with respect to k = 0. (c), (d) show fits of the corresponding data on the left to the model of a mixture of UDUD plaquettes, (e), prevailing at low temperature , and the UUUU (FM) plaquettes, (f), emergent on warming. spin resonance, were observed by different groups in various FeTe 1−x Se x samples, both with suppressed and welldeveloped superconductivity [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31]. In the absence of even a qualitative description, these results were often compared with ad-hoc functions, such as a Sato-Maki function, leading to data parameterizations void of much physical meaning [22]. "
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