Magnetic properties of the covalent chain antiferromagnetRbFeSe2

Abstract

Single crystals of the ternary iron selenide RbFeSe 2 have been investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, and specific-heat measurements as well as by Mössbauer spectroscopy. Built up from linear chains of edge-sharing FeSe 4 tetrahedra, RbFeSe 2 represents a quasi-one-dimensional antiferromagnet. Below T N = 248 K three-dimensional antiferromagnetic collinear magnetic order sets in, with the magnetic moments oriented perpendicularly to the chain direction. The hyperfine fields determined from our Mössbauer studies reveal strongly reduced magnetic moments. The high-temperature susceptibility data of RbFeSe 2 suggest a one-dimensional metallic character along the chains.

Incommensurate magnetism in K2MnS2−xSex and prospects for tunable frustration in a triangular lattice of pseudo-1D spin chains

“…The most closely-related compounds to the K 2 MnS 2 structure type are the family of AFeX 2 (A = K, Rb, Cs, Tl; X = S, Se) compounds, which can be divided into three groups based on their crystal and magnetic structures. [13] All AFeX 2 compounds have tetrahedrally co-arXiv:1905.03318v1 [cond-mat.mtrl-sci] 8 May 2019 ordinated Fe 3+ chains along c, but many of these have an additional degree of structural freedom, manifested as a monoclinic distortion (TlFeS 2 , TlFeSe 2 , KFeSe 2 , and RbFeSe 2 with the magnetic moments ordered perpendicular to the chains; and KFeS 2 , RbFeS 2 with the ordered moments slightly tilted from the chain axis). [14,15] Only CsFeS 2 is orthorhombic, but it further distorts martensitically at its magnetic transition at 70 K, with moments slightly tilted off the chain direction.…”

Cs[FeSe2], Cs3[FeSe2]2, and Cs7[Fe4Se8]: Missing Links of Known Chalcogenido Ferrate Series

“…in the Cs salts) as well as in Na[FeS 2 ] (I222) the parallel Q2 edges of all linear chains are at equal heights (Figure 3a, c, and d), whereas the edge positions of neighboring chains differ in the K and Rb phases of the KFeS 2 -type structure (C2/c, Figure 3b). In the latter structure, a nearly regular eight-coordination of A + is achieved, the effective coordination numbers ( 1 ECoN, [37,38] ), which are used throughout this work to quantify and compare the cation coordination, are also close to 8 Table 3). The Fe-Fe distances are also very similar, with values close to 270 pm for the sulfido and 280 to 283 pm for the selenido compounds (Reports on strongly alternating Fe-Fe distance along the chains, which still appear in recent works, [8] are not based on reliable crystal data).…”

“…In the latter structure, a nearly regular eight-coordination of A + is achieved, the effective coordination numbers ( 1 ECoN, [37,38] ), which are used throughout this work to quantify and compare the cation coordination, are also close to 8 Table 3). The Fe-Fe distances are also very similar, with values close to 270 pm for the sulfido and 280 to 283 pm for the selenido compounds (Reports on strongly alternating Fe-Fe distance along the chains, which still appear in recent works, [8] are not based on reliable crystal data). As expected, the coordination number of the A cations increases continuously from four (Na) via eight (K/Rb) to finally nine for the Cs title compound.…”

“…[1][2][3][4] The compounds with a Q:Fe ratio of 2:1 belong to two different classes: The large series of Fe III and Fe II/III mixed-valent chain ferrates exhibit hexagonal rod packings of linear or slightly buckled infinite chains of edge-sharing tetrahedra 1 ϱ [FeQ 4/2 ] n-. [5][6][7][8][9][10][11][12][4][5][6][7][8][9][10][11][12][13][14] The second class are salts containing cubane-type clusters . For numbers referring the structure type cf.…”

“…The general compound series A 1+x [Fe Figure 1): While oxido compounds of this type exhibit cristobalite-like networks of corner-sharing [FeO 4 ] tetrahedra, [20][21][22] the respective sulfido and selenido ferrates, which are observed for the whole alkali element series from Na (S) and K (Se) to Cs [5][6][7][8][9][4][5][6][7][8][9]23] contain linear chains of edge-sharing tetrahedra; tellurido ferrates(III) of this composition are unknown. The recently prepared first chain ferrates(II), Na 2 [FeS 2 ] and Na 2 [FeSe 2 ] [13,14] (x = 1, compound 5 in Figure 1), round out the series.…”