M\"{o}ssbauer study of the '11' iron-based superconductors parent compound Fe(1+x)Te

57Fe Moessbauer spectroscopy was applied to investigate the superconductor parent compound Fe(1+x)Te for x=0.06, 0.10, 0.14, 0.18 within the temperature range 4.2 K - 300 K. A spin density wave (SDW) within the iron atoms occupying regular tetrahedral sites was observed with the square root of the mean square amplitude at 4.2 K varying between 9.7 T and 15.7 T with increasing x. Three additional magnetic spectral components appeared due to the interstitial iron distributed over available sites between the Fe-Te layers. The excess iron showed hyperfine fields at approximately 16 T, 21 T and 49 T for three respective components at 4.2 K. The component with a large field of 49 T indicated the presence of isolated iron atoms with large localized magnetic moment in interstitial positions. Magnetic ordering of the interstitial iron disappeared in accordance with the fallout of the SDW with the increasing temperature

Hydrogen absorption and 57 Fe Mössbauer effect in UFeGe

Abstract. Hydrogenation of UFeGe transforms the monoclinic type of structure into the orthorhombic (TiNiSi-type) and subsequently to the hexagonal (ZrBeSi-type) structure. It does not induce magnetic order, however magnetic susceptibility is enhanced. The Sommerfeld coefficient γ increases from 12 mJ/mol K 2 in UFeGe to 36 mJ/mol K 2 in UFeGeH 1.7-1.8 (β-hydride). The observed variations of electronic properties are mainly due to the modified geometry of the lattice, characterized by enhanced inter-uranium spacing, and reduced 5f-3d hybridization in the hydrides

Moessbauer spectroscopy evidence for the lack of iron magnetic moment in superconducting FeSe

Superconducting FeSe has been investigated by measurements of the magnetic susceptibility versus temperature and Moessbauer spectroscopy at various temperatures including strong external magnetic fields applied to the absorber. It was found that isomer shift exhibits sharply defined increase at about 105 K leading to the lowering of the electron density on iron nucleus by 0.02 electron/a.u.^3. Above jump in the electron density is correlated with the transition from the P4/nmm to the Cmma structure, while decreasing temperature. Moessbauer measurements in the external magnetic field and for temperatures below transition to the superconducting state revealed null magnetic moment on iron atoms. Hence, the compound exhibits either Pauli paramagnetism or diamagnetic behavior. The principal component of the electric field gradient on the iron nucleus was found as negative on the iron site.Comment: 9 pages, 6 figures, 1 tabl

Charge and Spin Density Perturbation on Iron Nuclei by Non-Magnetic Impurities Substituted on the Iron Sites in α-Fe

The paper is aimed at the review of the charge and spin density perturbation on the iron nucleus in the bcc iron-based binary alloys containing as the impurity either 4d (Nb, Mo, Ru, Rh, Pd) or 5d (Os, Ir, Au) metals. Additionally, Ga was used as such impurity as well. Measurements were performed by means of the $\text{}^{57}Fe$ transmission Mössbauer spectroscopy at room temperature. Powder X-ray diffraction data for alloys investigated show linear dependence of the lattice constant versus impurity concentration. The Mössbauer data were treated assuming random distribution of the impurity over the iron sites and additive effect for the charge density perturbation, and additive in the algebraic sense effect for the corresponding spin density perturbation. Hence, the effect of impurity depends solely on the distance between impurity and the iron nucleus under above assumptions. It has been found that impurities being further away than a third or in some cases as the second neighbor do not contribute directly to the charge and spin perturbation. On the other hand, they have usually some minor effect on the average charge and spin density. Generally, the perturbation to either charge or spin density has some oscillatory character versus distance from the impurity. The phase and period of the charge oscillation is vastly different from the phase and period of the spin oscillation in the majority of cases. Substitution of the impurities with the increasing number of 4d or 5d electrons leads to the lowering of the electron density on the iron nucleus and causes decreased band spin density on this nucleus. Subsequent impurities donate more and more d-type electrons to the band, and the latter screen more and more effectively s-like electrons. Hence, the density of the s-like electrons on the iron nucleus diminishes. Impurities with 5d electrons have generally stronger effect on the charge and spin density perturbation than impurities with 4d electrons

Charge and Spin Density Perturbation on Iron Nuclei by Non-Magnetic Impurities Substituted on the Iron Sites in α-Fe

The paper is aimed at the review of the charge and spin density perturbation on the iron nucleus in the bcc iron-based binary alloys containing as the impurity either 4d (Nb, Mo, Ru, Rh, Pd) or 5d (Os, Ir, Au) metals. Additionally, Ga was used as such impurity as well. Measurements were performed by means of the $\text{}^{57}Fe$ transmission Mössbauer spectroscopy at room temperature. Powder X-ray diffraction data for alloys investigated show linear dependence of the lattice constant versus impurity concentration. The Mössbauer data were treated assuming random distribution of the impurity over the iron sites and additive effect for the charge density perturbation, and additive in the algebraic sense effect for the corresponding spin density perturbation. Hence, the effect of impurity depends solely on the distance between impurity and the iron nucleus under above assumptions. It has been found that impurities being further away than a third or in some cases as the second neighbor do not contribute directly to the charge and spin perturbation. On the other hand, they have usually some minor effect on the average charge and spin density. Generally, the perturbation to either charge or spin density has some oscillatory character versus distance from the impurity. The phase and period of the charge oscillation is vastly different from the phase and period of the spin oscillation in the majority of cases. Substitution of the impurities with the increasing number of 4d or 5d electrons leads to the lowering of the electron density on the iron nucleus and causes decreased band spin density on this nucleus. Subsequent impurities donate more and more d-type electrons to the band, and the latter screen more and more effectively s-like electrons. Hence, the density of the s-like electrons on the iron nucleus diminishes. Impurities with 5d electrons have generally stronger effect on the charge and spin density perturbation than impurities with 4d electrons

Feasibility study on the micro-foil internal conversion electron (MICE) detector application to high-temperature emission Mössbauer spectroscopy

Abstract Detailed calculations have been performed to assess potential applicability of the MICE-CEMS detector (CEMS -conversion electron Mössbauer spectroscopy) to the high temperature emission Mössbauer spectroscopy by means of the keV 41 . 14 transition in Fe 57 . The comparison was made with the standard transmission method using either proportional or semiconductor detector. It was found that for typical source matrices used in the investigations performed at high temperatures the MICE-CEMS detector yields poorer results than the high quality semiconductor detector. Therefore the development of the dedicated MICE-CEMS detector is unjustified for this particular application

Roughness Method to Estimate Fractal Dimension

A method based on the pattern roughness was introduced for determination of the fractal dimension and tested for fractals like the Sierpiński carpet, the Sierpiński triangle, standard Cantor set, the Menger sponge and the Sierpiński tetrahedron. It was tested for non-fractal pattern like two- and four-dimensional gray scale random dust as well. It was found that for all these patterns the Hausdorff dimension is reproduced with relatively high accuracy. Roughness method is based on simple, fast and easy to implement algorithm applicable in any topological dimension. It is particularly suited for patterns being composed of the hierarchy of structures having the same topological dimension as the space embedding them. It is applicable to "fuzzy" patterns with overlapping structures, where other methods are useless. It is designed for pixelized structures, the latter structures resulting as typical experimental data sets