Synthesis and Structures of New Layered Ternary Manganese Tellurides:  AMnTe₂ (A = K, Rb, Cs), Na₃Mn₄Te₆, and NaMn_1.56Te₂

Abstract

The synthesis and crystal structures of new ternary manganese tellurides, AMnTe2 (A = K, Rb, Cs), Na3Mn4Te6, and NaMn1.56Te2, are reported. These compounds are synthesized by solid-state reaction and cation exchange techniques in sealed Nb tubes. The single-crystal structures of AMnTe2 (A = K, Rb), Na3Mn4Te6, and NaMn1.56Te2 have been determined; KMnTe2: a = 4.5110(4) Å, c = 14.909(2) Å, I4̄m2 (No. 119, Z = 2); RbMnTe2: a = 4.539(1) Å, c = 15.055(2) Å, I4̄m2 (No. 119, Z = 2); Na3Mn4Te6: a = 8.274(4) Å, b = 14.083(6) Å, c = 7.608(6) Å, β = 91.97(4)°, C2/m (No. 12, Z = 2); NaMn1.56Te2: a = 4.4973(8) Å, c = 7.638(2) Å, P3̄m1 (No. 164, Z = 1). The fundamental building blocks of the title compounds are MnTe4 tetrahedra. AMnTe2 (A = K, Rb, Cs) are isostructural with TlFeS2, consisting of layers built up by four corner-shared MnTe4 tetrahedra. Manganese telluride layers in Na3Mn4Te6 consist of two hexagonal nets of Te atoms between which two-thirds of the tetrahedral interstices are filled with Mn atoms to form two 63 honeycomb nets. NaMn1.56Te2 adopts a defective CaAl2Si2 structure type, in which Mn atoms partially and randomly occupy 78% of tetrahedral sites. Temperature-dependent magnetic susceptibilities measurements show that AMnTe2 (A = K, Rb, Cs) exhibit Curie−Weiss paramagnetism, whereas Na3Mn4Te6 and NaMn1.56Te2 show paramagnetism with a weak dependence on temperature.

Structural, electronic and magnetic properties of the manganese telluride layers AMnTe2 (A = K, Rb, Cs) from first-principles calculations

“…The calculated values of the total spin magnetic moment per formula unit and the partial magnetic moments are listed in Most of the total spin magnetic moment is concentrated at the Mn atoms. The situation is similar to the well-known and widely studied NiMnSb semi-Heusler compound [17]. The…”

Synthesis and Structures of New Layered Ternary Manganese Selenides: AMnSe2 (A=Li, Na, K, Rb, Cs) and Na2Mn2Se3

“…These compounds exhibit polar [MnTe Te]\ layers, in which MnTe tetrahedra share three corners. Our subsequent systematic survey of A}Mn}Te systems (A" alkali metals)*an e!ort aimed at "nding other polar compounds*resulted in the synthesis of several new ternary tellurides, AMnTe (A"K, Rb, Cs), Na Mn Te , and NaMn Te (10). These new layered compounds, AMnTe (A"Li, Na), crystallizing in the noncentrosymmetric space group, P3m1 (No.…”

“…Of the re#ections, 140 were unique and 136 with I'2 (I) were used in the re"nements. RbMnSe in isostructural with the known phase RbMnTe , so the atomic positions of RbMnTe were used to begin re"nement (10). Isotropic re"nement showed reasonable thermal coe$cients for all atoms.…”

The new sodium tellurido manganates(II) Na2Mn2Te3, Na2Mn3Te4, Na2 AMnTe3 (A=K, Rb), and NaCsMnTe2

“…The structure of the mixed-valent tellurido phase NaMn 1.56 Te 2 exhibits a statistic occupation of the tetrahedral voids in an h.c.p. arrangement of tellurium ions [24]. The pure Li and Na manganates(III) AMnSe 2 [17] and AMnTe 2 [25] as well as the mixed-valent phase Na 3 Mn 4 Te 6 (25% Mn III , [24]) likewise contain h.c.p.…”

“…arrangement of tellurium ions [24]. The pure Li and Na manganates(III) AMnSe 2 [17] and AMnTe 2 [25] as well as the mixed-valent phase Na 3 Mn 4 Te 6 (25% Mn III , [24]) likewise contain h.c.p. chalcogen arrangements with layer-wise Mn-filled tetrahedral voids.…”