Structures and Physical Properties of Rare-Earth Zinc Antimonides Pr₆Zn_1+xSb_14+y and RE₆Zn_1+xSb₁₄ (RE = Sm, Gd−Ho)

Abstract

A new series of isostructural ternary rare-earth zinc antimonides RE(6)Zn(1+x)Sb(14+y) (RE = Pr, Sm, Gd-Ho) has been obtained by direct reaction of the elements at 1050-1100 degrees C. Single-crystal X-ray diffraction studies revealed that these compounds adopt an orthorhombic structure type (space group Immm (no. 71), Z = 2, a = 4.28-4.11 A, b = 15.15-14.73 A, c = 19.13-18.56 A in the progression from RE = Pr to Ho) that may be regarded as stuffed variants of a (U(0.5)Ho(0.5))(3)Sb(7)-type host structure. Columns of face-sharing RE(6) trigonal prisms, centered by Sb atoms, occupy channels defined by an extensive polyanionic Sb network. This network is constructed from three-atom-wide and four-atom-wide Sb strips, the latter being linked together by single Sb atoms in RE(6)Zn(1+x)Sb(14) (RE = Sm, Gd-Ho; y = 0), but also by additional Sb-Sb pairs in a disordered fashion in Pr(6)Zn(1+x)Sb(14+y) (y = approximately 0.6). Interstitial Zn atoms then partially fill tetrahedral sites (occupancy of 0.5-0.7) and, to a lesser extent, square pyramidal sites (occupancy of 0.04-0.12), accounting for the observed nonstoichiometry with variable x. Except for the Gd member, these compounds undergo antiferromagnetic ordering below T(N) < 9 K, with the magnetic susceptibilities of the Tb, Dy, and Ho members following the Curie-Weiss law above T(N). For the Ho member, the thermal conductivities are low and the Seebeck coefficients are small and positive, implying p-type character consistent with the occurrence of partial Zn occupancies. At low temperatures (down to 5 K), electrical resistivity measurements for the Tb, Dy, and Ho members indicated metallic behavior, which persists at high temperatures (up to 560 K) for the Ho member. Band structure calculations on an idealized "Gd(6)Zn(2)Sb(14)" model revealed the existence of a pseudogap near the Fermi level.

In-Phase Alignments of Asymmetric Building Units in Ln4GaSbS9(Ln = Pr, Nd, Sm, Gd−Ho) and Their Strong Nonlinear Optical Responses in Middle IR

“…The inverse magnetic susceptibility for Sm 4 GaSbS 9 does not follow the Curie−Weiss law (Figure b) and is typical for Sm 3+ -containing compounds, where spin−orbit coupling splits the 6 H ground term for Sm 3+ , leading to a temperature dependence of the effective moment from the 4f electrons. In general, these results are comparable to those found for Ln 6 Zn 1+ x Sb 14 , CsLnCdTe 3 , and ZnLn 6 Si 2 S 14 , which also show the antiferromagnetic ordering between the isolated Ln 3+ ions.…”

Ge Pairs and Sb Ribbons in Rare‐Earth Germanium Antimonides RE12Ge7−xSb21 (RE=La–Pr)

“…At 2 K, the magnetization approaches a saturation value of 1.2 μ B /Ce as the applied field is increased up to 70 000 Oe. In related compounds such as RE 6 Ge 5− x Sb 11+ x ,10b RE 6 MnSb 15 ,25 and RE 6 Zn 1+ x Sb 14 ,23c the presence of RE atoms within single columns of trigonal prisms gives rise to long‐range antiferromagnetic ordering with relatively low T N values (e.g., 4 K for Ce 6 Ge 5− x Sb 11+ x ), possibly as a result of a ferrimagnetic spin arrangement. The presence of larger assemblies of trigonal prisms in Ce 12 Ge 6.5 Sb 21 leads to more complex arrangements of Ce 4f moments that would have to be analyzed in detail through further experiments.…”

“…Further examples of the fascinating variations that can occur on this structural theme can also be found elsewhere. [23] It is not trivial to rationalize the bonding in RE 12 Ge 7Àx Sb 21 . If the substoichiometry in Ge is neglected, then the assumption of trivalent RE atoms fully donating their valence electrons leads to the difficult task of how to partition the 36À charge per formula unit over the anionic substructure [Ge 7 Sb 21 ].…”

A Ferrimagnetic Zintl Phase Pr4MnSb9: Synthesis, Structure, and Physical Properties

“…Compound Pr 4 MnSb 9 was first discovered in the reaction targeting at a proposed "Pr 6 Mn 1.2 Sb 14.6 ", an analogue of Pr 6 Zn 1.2 Sb 14.6 . 20 After establishing its structure, the pure phased Pr 4 MnSb 9 compound was synthesized by the stoichiometric reactions of Pr, Mn, and Sb elements in a carbon coated silica tube, which was flame-sealed under a vacuum of 10 −3 Pa. The reaction assembly was then heated in a temperature controlled tube furnace to 1373 at 25 K/ h, followed by dwelling for 20 h, and then cooling at 4 K/h to 373 K before shutting down the furnace.…”