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, RMAs 2 (R= Pr and Sm; M= Ag, Au), crystallizing in HfCuSi 2 -derived structure are reported. PrAgAs 2 orders antiferromagnetically at T N = 5 K. The Au analogue, 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 structure as that of former order magnetically nearly at the same temperature (about 17 K). It appears that, in PrAgAs 2 , SmAgAs 2 , and SmAuAs 2 , 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 PrAgAs 2 and PrAuAs 2 exhibits negative temperature coefficient in some temperature range in the paramagnetic state. SmAuAs 2 exhibits magnetic Brillouin-zone gap effect in ρ at T N , while SmAgAs 2 shows a well-defined broad minimum well above T N around 45 K. Thus, these compounds reveal interesting magnetic and transport properties. Introduction Following the discovery of superconductivity in the arsenide family in recent years, there have been explosive activities on arsenic containing transition-metal compounds. In particular, the ThCr 2 Si 2 -derived tetragonal compounds have attracted a lot of interest in this respect. The arsenic compounds with 1:1:2 composition, e.g., HfCuSi 2 -type layered structure [1-3] -a defective variant of the ThCr 2 Si 2 structure -however, has not been explored sufficiently for magnetic and superconducting anomalies, barring a few reports on Cu-based compounds RCuAs 2 (R = rare earth metals) [4][5][6][7][8]. Though corresponding Ag and Au-based compounds were also identified [8-10], very little work has been reported on these compounds. Considering that the Cu-based compounds, even for those rare-earths with 4f-stability, have been reported to exhibit interesting properties, we considered it worthwhile to probe these Ag and Au containing compounds as well. We believe that the knowledge thus gathered would eventually contribute to global understanding of the properties of the arsenide family. Among these Ag and Au compounds, interesting Kondo anomalies for Ce analogues have been reported in the recent literature [7]. Here we report the results of our investigation on the compounds PrMAs 2 and SmMAs 2 with M = Ag and Au. We find that the temperature (T) dependencies of the electrical resistivity (ρ) of these compounds are interesting and notso-commonly known for Pr and Sm compounds.

Quaternary rare-earth arsenides REAg1−Zn As2 (RE=La–Nd, Sm, Gd–Dy) with tetragonal SrZnBi2- and HfCuSi2-type structures

“…If conduction electrons are assumed to play a role in mediating the magnetic coupling between RE atoms, a more important effect may be that the Fermi level is adjusted on progressing from NdAgAs 2 to NdAg 0.5 Zn 0.5 As 2 . Related ternary arsenides REMAs 2 (M = Cu, Ag, Au) also tend to exhibit small negative Weiss parameters and the occurrence of antiferromagnetic ordering (typically at less than 10 K) seems to be quite sensitive to subtle structural features [46][47][48][49].…”

Giant Negative Magnetoresistance beyond Chiral Anomaly in Topological Material YCuAs2

“…Polycrystalline samples were synthesized by using conventional solid state reaction method. [ 41 ] Stoichiometric Y, Cu, and As were prereacted at 500 °C for 2 d, subsequently annealed at 900 °C for 10 d, and followed by furnace cooling. The obtained product was well crystallized with grey color and metallic luster.…”