Dependence of the structural, transport and magnetic properties of Tl1-yFe2-z(Se1-xSx)(2) with isovalent substitution of Se by S

作者：Toulemonde P^*; Santos Cottin D; Lepoittevin Ch; Strobel P; Marcus J

来源：Journal of Physics: Condensed Matter , 2013, 25(7): 075703.

DOI：10.1088/0953-8984/25/7/075703

The effect of selenium substitution by sulfur in the Tl1-yFe2-zSe2 antiferromagnet was studied by x-ray and electron diffraction, magnetization and transport measurements. Tl0.8Fe1.5.Se1-xSx)(2) (nominal composition) solid solution was synthesized in the full x range (0 <= x(S) <= 1) using the sealed tube technique. No superconductivity was found down to 4.2 K in the series despite the fact that the optimal crystallographic parameters, determined by Rietveld refinements, are reached in the series (i.e. the Fe-(Se, S) interplane height and (Se, S)-Fe-(Se, S) angle for which the critical superconducting transition T-c is usually maximal in pnictides). A quasi-full Tl site (y similar to 0.05) compared to significant alkaline deficiency (y = 0.2-0.3) in analogous A(1-y)Fe(2-z)Se(2) (A = K, Rb, Cs), and the resulting differences in iron valency, density of states and doping, are suggested as an explanation for this absence of superconductivity. Transmission electron microscopy confirmed the existence of an ordered iron vacancies network in the samples of the Tl0.8Fe1.5.Se1-xSx)(2) series in the form of the tetragonal root 5a x root 5a x c superstructure (I4/m). The Neel temperature (T-N) indicating the onset of antiferromagnetism order in this root 5a x root 5a x c supercell is found to decrease from 450 K in the selenide (x = 0) to 330 K in the sulfide (x = 1). Finally, we demonstrate a direct linear relationship between T-N and the Fe-(Se, S) bond length (or Fe-(Se, S) height).

• 出版日期2013-2-20