Single-crystal structure determination of two new ternary bismuthides: Rh6Mn5Bi18 and RhMnBi3.

Peter Kainzbauer,Martin C J Marker,Klaus W Richter,Herta Silvia Effenberger,Herbert Ipser

doi:10.1107/s2053229618009087

Peter Kainzbauer, Martin C J Marker + Show 3 more

Open Access

https://doi.org/10.1107/s2053229618009087

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Abstract

A study of the ternary Rh-Mn-Bi phase diagram revealed the existence of two new ternary bismuthides, viz. hexarhodium pentamanganese octadecabismuthide (Rh6Mn5Bi18) and rhodium manganese tribismuthide (RhMnBi3). Their crystal structures represent new structure types. Rh6Mn5Bi18, with a Wyckoff sequence a f2 g2 i5, crystallizes in the tetragonal system (space group P42/mnm; Pearson symbol tP58), and RhMnBi3, with a Wyckoff sequence a c g i q, crystallizes in the orthorhombic system (Cmmm; oS20). In the Rh6Mn5Bi18 structure, the transition metal atoms are linked into ribbon-like structural units aligned along the [001] direction, whereas planar sheets are formed in RhMnBi3. In both crystal structures, the units formed by the transition metal atoms are enveloped by Bi atoms, which themselves form a loosely bound network. The linkage results in a layer structure for RhMnBi3, while in the case of Rh6Mn5Bi18, a three-dimensional network is formed; the latter, however, contains several areas where Bi...Bi distances suggest van der Waals interactions. Both phases under discussion have analogous structural motifs.

Highlights

There has been an ongoing search for ferromagnetic materials free of rare earth elements
A possible approach to circumvent these problems was considered to be the addition of a third component, e.g. Rh, which forms an intermetallic phase with Bi that is isotypic with -BiMn (Ross & Hume-Rothery, 1962; Kainzbauer et al, 2018)
A systematic study of the ternary Rh–Mn–Bi system at different temperatures was considered of interest, with the focus on finding additional intermetallic phases which might possibly exhibit ferromagnetism

Summary

Introduction

There has been an ongoing search for ferromagnetic materials free of rare earth elements. Street et al (1974) identified a ferromagnetic compound, i.e. Mn5Rh2Bi4 (cubic, Fm3m), with a Curie temperature of 266 K. A similar observation was made by Taufour et al (2015), who described the ferromagnetic compound Mn1.05Rh0.02Bi, with a Curie temperature below 416 K. Suits (1975) discovered ferromagnetism in Bi-substituted RhMn with the composition RhMn0.8Bi0.2. Based on these observations, a systematic study of the ternary Rh–Mn–Bi system at different temperatures was considered of interest, with the focus on finding additional intermetallic phases which might possibly exhibit ferromagnetism. It may be of particular interest that Rh6Mn5Bi18 is probably one of the first reported ternary manganese pnictide phases, with a network formed by Bi atoms where alkaline or rare earth metal elements are absent. Further examples are known to crystallize in the cubic structure type Cu4Mn3Bi4 (Street et al, 1974; Szytula et al, 1981)

Synthesis and crystallization

Refinement

Results and discussion