Dy117Co57Sn112, a new structure type of ternary intermetallic stannides with a giant unit cell

Synthesis, Crystal Structure, and Magnetic Properties of Giant Unit Cell Intermetallics R117Co52+δSn112+γ (R = Y, La, Pr, Nd, Ho)

“…Y 117 Co 56 Sn 115 , similar to Dy 117 Co 57 Sn 112 [24], displays a relatively ordered structure as compared to the reported Sm-, Gd-, and Tb-containing analogues [23,27] (Table 2). All the Y and Sn positions are fully occupied, as opposed to the latter three structures which exhibit partial occupancy or splitting in some of the R and Sn sites.…”

“…The disorder of the Co2 and Co3 sites is common to all reported R 117 Co 52+δ Sn 112+γ compounds. Also common is the mixed occupancy of the 32f Wyckoff positions by cobalt and tin atoms (Co51/Sn52), although in the Dy-and Pr-containing analogues this site was reported to be occupied solely by cobalt [24,25]. Crystals 2016, 6, 165 4 of 12 meaningful structure should avoid the coexistence of the cubic apex and its surrounding trigonal apex, so the actual configuration is built of the yttrium-centered distorted cuboctahedron (DCBO) of Co3 sites that is penetrated by a tetrahedron of Co2 sites, where the Co2-Co2 and Co2-Co3 distances are 2.71 and 2.38 Å, respectively ( Figure 3b).…”

“…The disorder of the Co2 and Co3 sites is common to all reported R117Co52+δSn112+γ compounds. Also common is the mixed occupancy of the 32f Wyckoff positions by cobalt and tin atoms (Co51/Sn52), although in the Dy-and Pr-containing analogues this site was reported to be occupied solely by cobalt [24,25]. (6) Arguably, the most interesting crystallographic changes take place in the TOH A, and these changes are related to the size of the lanthanide atom.…”

“…In all R117Co52+δSn112+γ structures, at the center of the TOH A is the Wyckoff site 4b surrounded by a cube of Sn atoms ( Figure 4). Interestingly, this site is never occupied in the Tb117Fe52Ge112-type germanides, which led Mudryk et al to suggest that the stannides should be considered as a separate Dy117Co57Sn112 structure type [28], according to the first reported representative of this family [24]. As the radius of the R atom increases upon going from Y to Dy and then to La along the lanthanide series, the increase in the unit cell parameter a causes larger Sn-Sn separation in the cube of Sn atoms that surround the 4b site (Table 3).…”

“…In terms of physical properties, only the basic magnetism studies for R 117 Co 52+δ Sn 112+γ (R = Pr, Ce, Sm, Tb, Dy) [23][24][25]28] and Pr 117 Co 56. 7 Ge 112 [29], plus a relatively complete physical property investigation for Gd 117 Co 56 Sn 114 [27,28], have been reported.…”