The Solid Solutions (Ce_1-xLa_x)RuSn

Abstract

X-Ray-pure samples of the solid solutions (Ce 1−x La x )RuSn were obtained up to x = 0.5. Powder diffraction data show the CeRuSn-type superstructure up to x ≈ 0.3 and the CeCoAl-type subcell for higher lanthanum contents. The structure of a single crystal with x = 0.5 was refined on the basis of single-crystal X-ray diffractometer data: CeCoAl type, C2/m, a = 1160.8(2), b = 477.6(1), c = 511.6(1) pm, β = 102.97(2) • , wR = 0.0510, 444 F 2 values, 20 variables. Magnetic investigations were performed for all samples up to a lanthanum content of x = 0.4. No cooperative phenomena could be observed, and all samples show Curie-Weiss behavior above a certain temperature. The cerium valence is about 3.32(2) for all samples of the solid solution. Hence, La 3+ has to replace Ce 3+ as well as Ce 4+ in a particular quantity. The electrical resistivity measurements confirm the suppression of the magnetic ordering and the structural transition upon replacement of cerium by lanthanum. 119 Sn Mössbauer spectra of samples with x = 0.2 and 0.5 are indicative of single tin sites with isomer shifts of δ = 1.86(1) mm s −1 for x = 0.2 and δ = 1.88(1) mm s −1 for x = 0.5. Both signals are subject to significant quadrupole splitting, a consequence of the low site symmetry. Results of XANES measurements are perfectly in line with the cerium valences determined by susceptibility measurements and yield a constant value of 3.16(1) for all investigated compounds.

A ZrNiAl related high-pressure modification of CeRuSn

“…13. Similar values have already been reported for other valence fluctuating compounds, 62,73 confirming the results from the magnetic investigations.…”

“…However, comparison of HP-CeRuSn with different solid solutions CeRu 1−x T x Sn (T = Rh, Ni, Pd, Pt). [61][62][63] compromises the abovementioned assumption of trivalent cerium in HP-CeRuSn. Intermediate cerium valence is proven by magnetic susceptibility and XANES measurements for these solid solutions, while almost identical distances are observed.…”

“…The main characteristic of the inverse magnetic susceptibility is a non-linear temperature dependence as it would be expected for a trivalent cerium compound according to the Curie-Weiss law. As a consequence thereof, a fitting with an ICF-model (Interconfiguration fluctuation) 62,63,69,70 has been performed and led to fitting parameters of E ex /k B = 1258(1) K, T sf = 877(2) K, n = 0.037(1), and χ 0 = 1.77 × 10 −4 emu mol −1 . Note that the temperature independent susceptibility χ 0 was fixed in the last refinement steps to prevent over-determination.…”