RFe2MgxAl8−x (R=La–Nd and Sm; x≈0.8): Flux synthesis, structure, magnetic and electrical properties

Abstract

Single crystals of Mg-substituted CeFe2Al8 type intermetallics RFe2MgxAl8–x (R=La–Nd and Sm; x≤1) were grown by reacting iron and rare earth metals in 1:1 Mg/Al mixed flux. The structure features mono-capped and bi-capped trigonal prismatic FeAl6 units. Electronic structure calculations indicate that magnesium substitution reduces the valence electron count, shifting the Fermi level away from a pseudo-gap. This changes the electronic nature of the cerium analog; the previously reported ternary CeFe2Al8 shows strong hybridization between the cerium states and the conduction electrons, resulting in no magnetic moment on Ce atoms. On the other hand, magnetic susceptibility measurements on CeFe2MgxAl8–x indicates a localized moment on cerium. The newly synthesized Pr, Nd and Sm analogs exhibit antiferromagnetic ordering at 2.8K, 7.8K and 12K respectively. Solid state 27Al NMR of LaFe2MgxAl8–x exhibits a broad Knight shift at ~1200ppm, consistent with the metallic behavior shown by electrical resistivity data.