Crystal structure, 57Fe Mössbauer spectroscopy and magnetization of UxFe6Sn6 (0≤x≤0.6)

Dependence of the Fe anisotropy on the Dy concentration in the DyxFe6Sn6 (0.3<x<1) compounds

“…3) are clearly different from those of DyFe 6 Sn 6 or of Dy 0.5 Fe 6 Sn 6 at 10 K. They have features similar to those reported for FeSn [17,18], YbFe 6 Ge 6 at 4 K [19], Yb 0.6 Fe 6 Sn 6 [9], U x Fe 6 Sn 6 (0 < x < 0.6) [11]. On the other hand, labeling the six lines Table 1 Estimated parameters from the Mössbauer spectra of Dy x Fe 6 Sn 6 (0.3 ≤ x ≤ 1) taken at different temperatures T observed in the 295 K spectrum of Dy 0.5 Fe 6 Sn 6 from 1 to 6 from negative to positive velocities, peaks 1 and 5 appear to be narrower than peaks 2 and 6, respectively, as also found for A x Fe 6 Sn 6 (A = Sc, Zr, Tm, Yb, Lu) [9,12].…”

“…As previously explained in detail [11,18,19] when the µ Fe direction is parallel to the c-axis a single sextet is observed, but when µ Fe deviates from this direction three different sextets are observed for the crystallographic equivalent Fe atoms as reported for FeSn [17,18], YbFe 6 Ge 6 at 4 K [19], Yb 0.6 Fe 6 Sn 6 [9], U x Fe 6 Sn 6 (0 < x < 0.6) [11].…”

“…For the smaller A = Sc, Zr, Tm, Lu, however, under stoichiometry of A was found to induce a local magnetic disorder where a few µ Fe are no longer lying along the c-axis but pointing along directions between the basal plane and the c-axis [12]. Finally for A = Yb and U the corresponding anisotropy is clearly different from that in the other AFe 6 Sn 6 compounds and similar to that in FeSn [9,11]. It should however be noted that in these compounds the concentration of A is lower than 0.6 atoms per f.u.…”

“…As calculated for the binary CoSn-type FeX parent compounds [17,18] there are three sets of principal EFG axes for the three iron atoms of each (0 0 1) Fe layer in a unit cell. The similarity of the Mössbauer spectra of Yb 0.6 Fe 6 Sn 6 and U x Fe 6 Sn 6 with those of AFe 6 Ge 6 , where µ Fe were found to lie in the ab-plane by neutron diffraction, led to the conclusion that in Yb 0.6 Fe 6 Sn 6 and U x Fe 6 Sn 6 V zz also lies in the ab-plane [9,11].…”

“…The smaller A, such as Tm, Yb, Lu and U are incorporated, in an ordered fashion, in half of the Fe-X-Fe slabs of the binary parent compound leading to the HfFe 6 Ge 6 -type structure (with the same P6/mmm space-group). When X = Sn it has further been shown that less than 1 A atom per 6 Fe + 6 X may be inserted, giving rise to a defect isotype of the SmMn 6 Sn 6 -type of structure, a partially disordered variant of this structure type [9][10][11]. In the case of the larger A elements that form AFe 6 X 6 compounds (A = Y, Gd-Er for X = Sn), long-range A atomic ordering leads to the formation of various superstructures, depending on A and on the annealing history [7].…”