Magnetic and electrical transport anomalies of RMAs₂ (R = Pr and Sm, M = Ag and Au)

Abstract

The results of magnetization, heat capacity and electrical resistivity (ρ) studies of the compounds RMAs₂ (R = Pr and Sm; M = Ag, Au), crystallizing in an HfCuSi₂-derived structure, are reported. PrAgAs₂ orders antiferromagnetically at T_N = 5 K. The Au analog, however, does not exhibit long range magnetic order down to 1.8 K. We infer that this is due to subtle differences in their crystallographic features, particularly noting that both the Sm compounds with identical crystal structures as that of the former order magnetically nearly at the same temperature (about 17 K). It appears that, in PrAgAs₂, SmAgAs₂ and SmAuAs₂, there is an additional magnetic transition at a lower temperature, as though the similarity in the crystal structure results in similarities in magnetism as well. The ρ for PrAgAs₂ and PrAuAs₂ exhibits a negative temperature coefficient in some temperature range in the paramagnetic state. SmAuAs₂ exhibits a magnetic _{Brillouin-zone} gap effect in ρ at T_N, while SmAgAs₂ shows a well-defined broad minimum well above T_N around 45 K. Thus, these compounds reveal interesting magnetic and transport properties.