Pr 62 Fe 21 M 16 C 32 Versus Pr 21 Fe 8 M 7 ' C 12 (M = Si, P; M' = Si, Ge, Sn): Competing Intermetallic Carbides Grown from a Pr/Ni Flux

• Published in: Inorganic chemistry Vol. 58; no. 1; pp. 540 - 548
• Main Authors: Engstrand, Tate O, Latturner, Susan E
• Format: Journal Article
• Language: English
• Published: United States 07.01.2019
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.8b02741

Reactions of silicon, carbon, and iron in a low-melting flux mixture of praseodymium and nickel produced two competing intermetallic compounds. Pr Fe Si C has a new structure type in tetragonal space group P4/ mmm ( a = 15.584(2) Å, c = 11.330(1) Å, Z = 1) that features trigonal planar FeC units that share corners to form a framework of cylindrical channels encompassing a network of silicon-centered praseodymium clusters. Slight variation of reactant ratio and heating profile produced Pr Fe Si C instead; this compound has the previously reported cubic La Fe Sn C structure type. Identical Pr/Si clusters and FeC subunit motifs are found in both structure types. In addition to reactant ratio and heating profile, size effects play a role in determining which structure forms. Replacing silicon with smaller phosphorus atoms produces only the tetragonal structure; replacement with larger elements (M = Ge, Sn) yields only cubic Pr Fe M C . Magnetic susceptibility measurements on single crystals of Pr Fe Si C indicate antiferromagnetic ordering of the Pr moments below 17 K and no magnetic moment on iron atoms. The behavior of Pr Fe Si C is more complex, revealing magnetic contributions from both Pr and Fe atoms and possible spin frustration.