The Solid Solutions (Ce1-xLax)RuSn

X-Ray-pure samples of the solid solutions (Ce1-xLax)RuSn were obtained up to x = 0.5. Powder diffraction data show the CeRuSn-type superstructure up to x approximate to 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, beta = 102.97(2)degrees, 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, La3+ has to replace Ce(3+)as well as Ce4+ 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. Sn-119 Mossbauer spectra of samples with x = 0.2 and 0.5 are indicative of single tin sites with isomer shifts of delta = 1.86(1) mm s(-1) for x = 0.2 and delta = 1.88(1) nun 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.