Structural transition and antiferromagnetic ordering in the solid solution CePd1-xAuxAl (x=0.1-0.9)

摘要

The intermetallic solid solution CePd1-xAuxAl (x = 0.1-0.9) has been synthesized from the elements by arc-melting and subsequent annealing in induction followed by tube furnaces. The samples were characterized using the Guinier powder diffraction technique and the structures of the nominal compositions CeAnAl and CePd(0.2)AU(0.8)Al were refined from single crystal X-ray diffractometer data. For small values of x = 0.1-0.3, the compounds crystallize in the hexagonal ZrNiAl-type structure (space group P (6) over bar 2m), while for x = 0.5-0.9 the orthorhombic TiNiSi-type structure (space group Pnma) was observed. In both structure types, the transition metal and aluminum atoms form a complex polyanionic network with the cerium atoms filling the respective cavities. The transition metal atoms are in both cases surrounded in the shape of a tri-capped trigonal prism, the connectivity of these units, however, is different. Temperature-dependent magnetic susceptibility measurements of all compounds indicated a stable trivalent oxidation state for the cerium atoms along with antiferromagnetic ordering around T-N similar to 3 K.