MgAgAs-type structure

MgAgAs structure type. See fig. 37, table 37. SG F43m, Z = 4, a = 0.6055 nm for ScNiSb (Pecharsky etal., 1983a, 1983b). 

Number 1 corresponds to AIB2 structure type 2 - ZrBeSi 3 - MgAgAs 4 - Caln2 5 - TiNiSi 6 - LiGaGe 7-KHg2 8-CeScSi. 

Sm-PtSb. SmPtSb crystallizes with the MgAgAs-type structure, a = 0.6554 (Rossi et al 1981 powder X-ray diffraction data). For the experimental details, see the LaPtSb system. 

Gd-Pt-Sb. The X-ray powder analysis oftheGdPtSb compound showed that it had the MgAgAs type structure with a = 0.6585 (Dwight, 1974). For the sample preparation, see ScNiSb. 

An early investigation of the TbNiSb compound showed that it had the MgAgAs-type with a = 0.6327 (Dwight, 1974), from an X-ray powder analysis of an alloy arc melted under argon and annealed at 973 K. Pecharsky et al. (1983a) and Hartjes and Jeitschko (1995) confirmed the crystal structure and obtained the lattice parameters as a = 0.6302 and a = 0.6304, respectively, by X-ray powder diffraction. For experimental details, see ScNiSb and LaNiSb respectively. 

Er-Pd-Sb. Marazza et al. (1980) established the MgAgAs type structure with a = 0.6467 for the ErPdSb compound by using X-ray powder diffraction and metallographic analyses. For the sample preparation and the purity of the starting components, see Y-Pd-Sb system. 

Preliminary results on low temperature transport properties in YbPdSb system with MgAgAs type structure are presented by Aliev et al. (1988). Resistivity shows a maximum at T = 50-100 K and the Fermi-liquid decrease of q go + AT2 at helium temperatures. The high value of the A coefficient 5 p 2 cm/K2 indicates the possibility of the heavy fermion behavior with y about 300MOO mJ/molK2. The Seebeck coefficient S is positive and shows a maximum Smax 22 pV/K at T 200 K. 

Fig. 4.24. Schematic drawing of the MgAgAs-type cubic structure adopted by some AnTX compounds.

The structural similarity of MgAgAs-type compounds with Heusler alloys and with the transition-metal based half-metallic ferromagnets (de Groot et al. 1983) has provoked band-structure calculations of UNiSn (Mueller et al. 1987, Albers et al. 1987). Self-consistent-field scalar relativistic spin-polarized calculations neglecting the spin-orbit coupling revealed the following features of the valence band ... 

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