TERNARY COMPOUNDS REAGSB(2), RE=Y, LA, CE, PR, ND, SM, GD, TB, DY, HO, ER, TM - MAGNETISM AND CRYSTAL-STRUCTURE

Ternary compounds REAgSb(2), RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, have been synthesized by are melting followed by a heat treatment at 600 or 800 degrees C for 300 hr. The novel phases were all found to be isotypic with the structure type of ZrCuSi2. Precise atom parameters have been derived for CeAgSb2 from X-ray single crystal counter data: space group P4/nmm, a = 0.43641(9) mn, c = 1.0722(4) mm, and Z = 2. For 274 reflections (\F-o\ > 3 sigma) the residual values are R(F) = Sigma\Delta F\/Sigma\F-o\ = 0.024 and R(W) = 0.028. A standardized set of atom parameters is provided. Magnetism of the REAgSb(2) phases in the temperature range 2.5 to 300 K is characterized by tripositive paramagnetic behavior of the rare-earth atoms. REAgSb(2) with RE = Y, La are weakly temperature-dependent paramagnets. In contrast, REAgSb(2) compounds with RE = Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm are weak antiferromagnets with ordering temperatures lower than T-N similar to 13 K, and CeAgSb2 is a noncolinear antiferromagnet (T-M similar to 12 K) with a remanent magnetization mu = 0.15 mu(B) per Ce atom. (C) 1995 Academic Press, Inc.