Interplay of disorder and antiferromagnetism in TIFe sub(1.6+ delta )(Se sub(1-x)S sub(x)) sub(2) probed by neutron scattering

• Published in: Journal of physics. Condensed matter 2014-07, Vol.26 (27), p.1-10
• Main Authors: Carlsson, S J E, Santos-Cottin, D, Lepoittevin, Ch, Strobel, P, Nassif, V, Suard, E, Toulemonde, P
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Iron; Neutron scattering; Order disorder; Sulfides; Sulfur; Sulphur; Vacancies
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/26/27/275701

The effect of selenium substitution by sulphur on the structural and physical properties of antiferromagnetic TIFe sub(1.6+ delta )Se sub(2) has been investigated via neutron, x-ray and electron diffraction, and transport measurements. The [radical]5a x [radical]5a x c super-cell related to the iron vacancy ordering found in the pure TIFe sub(1.6)Se sub(2) selenide is also present in the S-doped TIFe sub(1.6+ delta )(Se sub(1-x)S sub(x)) sub(2) compounds. Neutron scattering experiments show the occurrence of the same long range magnetic ordering in the whole series i.e. the 'block checkerboard' antiferromagnetic structure. In particular, this is the first detailed study where the crystal structure and the [radical]5 a x [radical]5 a antiferromagnetic structure is characterized by neutron powder diffraction for the pure TIFe sub(1.6+ delta )S sub(2) sulphide over a large temperature range. We demonstrate the strong correlation between occupancies of the crystallographic iron sites, the level of iron vacancy ordering and the occurrence of block antiferromagnetism in the sulphur series. Introducing S into the Se sites also increases the Fe content in TIFe sub(1.6+ delta )(Se sub(1-x)S sub(x)) sub(2) which in turn leads to the disappearance of the Fe vacancy ordering at x = 0.5 + or - 0.15. However, by reducing the nominal Fe content, the same [radical]5 a x [radical]5 a x c vacancy ordering and antiferromagnetic order can be recovered also in the pure TIFe sub(1.6+ delta )S sub(2) sulphide with a simultaneous reduction in the Neel temperature from 435K in the selenide TIF sub(1.75)Se sub(2) to 330 K in the sulphide TIFe sub(1.5)S sub(2). The magnetic moment remains high at low temperature throughout the full substitution range, which contributes to the absence of superconductivity in these compounds.