CeAgAs₂ — a New Derivative of the HfCuSi₂ Type of Structure: Synthesis, Crystal Structure and Magnetic Properties

Abstract

Single crystals of CeAgAs2 have been obtained by chemical transport reactions starting from a pre‐reacted powder sample. The crystal structure was solved using X‐ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Å, b = 5.7852(4) Å, c = 21.066(3) Å, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs2 represents a new distorted and ordered variant of the HfCuSi2 type. The characteristic feature of this structure are infinite cis‐trans chains of As atoms with As—As distances of 2.563(1) Å and 2.601(1) Å. CeAgAs2 is paramagnetic (μeff = 2.37 μB, θ = —10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K.

Intriguing magnetic and electrical transport behavior in novel CeTAs2 (T=Cu, Ag, Au) compounds

“…Similarly, for CeAgAs 2 we corroborate Curie-Weiss character of the magnetic susceptibility above 50 K, reported in Ref. [6]. In contrast to the latter study the sample measured in the present work showed the presence of two features in χ(T), at T N = 6 K and T m = 4.8 K, instead of a single peak at 5.5 K. As displayed in Fig.…”

“…However, in the case of CeAgAs 2 a few reflections showed some small splitting indicative of orthorhombic distortion, as already reported for this compound in Ref. [6]. No foreign lines were observed in any of the diffraction patterns thus proving single-phase character of the samples used for physical properties studies.…”

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

“…Some ternary rare-earth transition-metal pnictides REM 1-x Pn 2 with SrZnBi 2 -or HfCuSi 2 -type structures are subject to distortion of a square net of Pn atoms [16,[21][22][23][24][25]. This phenomenon is often signalled by abnormally large displacement ellipsoids of the Pn2 site within the parent tetragonal structure.…”

“…Indeed, the most prevalent ternary rare-earth transition-metal pnictides are HfCuSi 2 -type phases REM 1-x Pn 2 , where the M site is generally defective if it is occupied by a d-block element other than a monovalent one (i.e., from the Cu triad) [9][10][11]. Among arsenides, the only known representatives thus far are REMAs 2 (M = Cu [12,13], Ag [14][15][16], Au [15]), which are stoichiometric, and REZn 1-x As 2 , which are substoichiometric (REZn 0.67 As 2 ) [17,18]. However, a small Cu excess can be accommodated in lightly stuffed HfCuSi 2 -type phases RECu 1.1 As 2 [19,20].…”

“…However, a small Cu excess can be accommodated in lightly stuffed HfCuSi 2 -type phases RECu 1.1 As 2 [19,20]. Structural complications are possible because these phases can be subject to symmetry-lowering distortions within square nets of Pn atoms [16,[21][22][23][24][25] and vacancy ordering within the M sites [17].…”