57Fe Mössbauer study of Lu2Fe3Si5 iron silicide superconductor

Abstract

With the advent of Fe-As based superconductivity it has become important to study how superconductivity manifests itself in details of 57 Fe Mössbauer spectroscopy of conventional, Fe -bearing superconductors. To this end, the iron-based superconductor Lu2Fe3Si5 has been studied by 57 Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc = 6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. The value of Debye temperature was estimated from temperature dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed.

57Fe Mössbauer and magnetic studies of Th7Co2.5 57Fe0.5 and Th7Ni2.5 57Fe0.5 superconductors

“…We can notice that the θ D values estimated from IS(T) and C(T) dependences differ between themselves. Such disagreement is not surprising since a similar differences were reported earlier in Mössbauer studies of FeSe 0.5 Te 0.5 [14], 57 Fe-dopedYBa 2 Cu 3 O 6.8 [24], Lu 2 Fe 3 Si 5 [25] or CaKFe 4 As 4 and KFe 2 As 2 [26] compounds. This discrepancy may be explained by the fact that the area C reflects the average mean-square vibrational displacements, while IS is related to the mean-square velocity of the Mössbauer atom.…”

$^{57}$Fe Mössbauer study of stoichiometric iron based superconductor CaKFe$_4$As$_4$: a comparison to KFe$_2$As$_2$ and CaFe$_2$As$_2$

“…Although part of this discrepancy could be due to deviations from the thin absorber conditions of the measurements, it should be mentioned that similar differences were found earlier in studies of Lu 2 Fe 3 Si 5 , FeSe 0.5 Te 0.5 and 57 Fe doped YBa 2 Cu 3 O 6.8 compounds. [7,38,39] This discrepancy may be explained by the fact the area reflects the average mean-square displacements, whereas IS is related to the mean-square velocity of the Mössbauer atom. Both quantities may respond in a different way to lattice anharmonicities.…”

“…Historically, this technique has been applied to studies of superconductors for decades, [6] however its sensitivity specifically to the superconducting state is ambiguous. [7] It is quite natural that Mössbauer spectroscopy was widely used for studies of iron-based superconductors that naturally contain the common Mössbauer nuclide, 57 Fe, in the structure, [8,9,10,11,12]: no additional doping with 57 Fe (that can alter the properties of the material) is needed, and use of partially enriched Fe was required in only few, very specific cases. This technique was very successful in addressing the evolution of magnetic order, [13] structural phase transitions, [14] and phase purity [15,16,17] in these materials.…”