Syntheses, Structure, and Selected Physical Properties of CsLnMnSe₃ (Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y) and AYbZnQ₃ (A = Rb, Cs; Q = S, Se, Te)

Abstract

CsLnMnSe(3) (Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y) and AYbZnQ(3) (A = Rb, Cs; Q = S, Se, Te) have been synthesized from solid-state reactions at temperatures in excess 1173 K. These isostructural materials crystallize in the layered KZrCuS(3) structure type in the orthorhombic space group Cmcm. The structure is composed of LnQ(6) octahedra and MQ(4) tetrahedra that share edges to form [LnMQ(3)] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing AQ(8) bicapped trigonal prisms. There are no Q-Q bonds in the structure of the ALnMQ(3) compounds so the formal oxidation states of A/Ln/M/Q are 1+/3+/2+/2-. The CsLnMnSe(3) materials, with the exception of CsYbMnSe(3), are Curie-Weiss paramagnets between 5 and 300 K. The magnetic susceptibility data for CsYbZnS(3), RbYbZnSe(3), and CsYbMSe(3) (M = Mn, Zn) show a weak cusp at approximately 10 K and pronounced differences between field-cooled and zero-field-cooled data. However, CsYbZnSe(3) is not an antiferromagnet because a neutron diffraction study indicates that CsYbZnSe(3) shows neither long-range magnetic ordering nor a phase change between 4 and 295 K. Nor is the compound a spin glass because the transition at 10 K does not depend on ac frequency. The optical band gaps of the (010) and (001) crystal faces for CsYbMnSe(3) are 1.60 and 1.59 eV, respectively; the optical band of the (010) crystal faces for CsYbZnS(3) and RbYbZnSe(3) are 2.61 and 2.07 eV, respectively.

Quaternary rare-earth selenides with closed cavities: Cs[RE9Mn4Se18] (RE = Ho–Lu)

“…6. 19 The magnetic interactions should occur mainly between the centers M-M or RE-M (the nearest distance is around 3.90 Å). The theoretical total effective magnetic moment can be calculated by the equation μ eff (cal.)…”

Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

“…Previous compounds have most commonly contained the [Hg 6 As 4 ] moiety, but other known structural fragments include [Hg 7 As 4 ], [HgAs 2 ], [Hg 3 As 2 ], [Hg 11 As 4 ], [Hg 23 As 12 ], and [Hg 13 As 8 ]. All examples of the [Hg 6 As 4 ] structural moiety contain As-As bonding in the form of As framework.…”

“…Rather, there are 2 1 ½Hg 6 As 4 layers with Hg 6 As 6 rings that are interconnected in the [001] direction alternately by Hg 2 2+ and Hg 3 2+ units. The [Hg 23 As 12 ] [35] moiety contains one As 2 4À dumbbell per 12 As atoms and has equivalent cavities. The [Hg 13 As 8 ] [35] moiety contains three As 2 4À dumbbells per eight As atoms, and has nonequivalent cavities.…”

CsYbSe2

“…Each Yb atom is surrounded by a slightly distorted octahedron of six Se atoms. The YbÐSe distance of 2.8432 (5) A Ê is also comparable to those of 2.8360 (5)±2.8659 (5) A Ê in CsYbMnSe 3 (Mitchell et al, 2004).…”

“…Each Cs atom is surrounded by a trigonal prism of six Se atoms. The CsÐSe distance of 3.5370 (6) A Ê is comparable to those of 3.5926 (8)± 3.8173 (8) A Ê in CsYbMnSe 3 (Mitchell et al, 2004). Each Yb atom is surrounded by a slightly distorted octahedron of six Se atoms.…”