Magnetism and electronic correlations in the iron aluminides R Fe₂Al₁₀ (R = Y, Yb)

YFe₂Al₁₀ and YbFe₂Al₁₀ are new additions to the currently investigated rare-earth (R) series of compounds RT₂Al₁₀ in which T is Fe, Ru, or Os. Unusual physical properties are drawing considerable attention to this group of compounds. Intriguingly, very small moments order in CeRu₂Al₁₀ at as high as 27 K, whereas CeFe₂Al₁₀ is a Kondo insulator with very strong hybridization of the Ce magnetic moments and no magnetic ordering at all. Here we present the first results of two further iron-based compounds YFe₂Al₁₀ and YbFe₂Al₁₀ as a timely contribution to the knowledge of the physics at work in this system. In YFe₂Al₁₀ we find signatures of correlated electrons and the low-temperature results of specific heat, magnetic susceptibility and electrical resistivity are indicative of ferromagnetic quantum criticality. In YbFe₂Al₁₀ localized f-electron spins of Yb become involved in correlations with a moderately enhanced electronic specific heat that classifies it as a non-ordered heavy-fermion compound. Unusual physical properties are drawing considerable attention to the RT₂Al₁₀ group of compounds (R = rare earth, T = Fe, Ru, or Os). The authors present first results for two further iron-based compounds of this group, YFe₂Al₁₀ and YbFe₂Al₁₀, as a timely contribution to the knowledge of the physics at work in this system. In YFe₂Al₁₀ they find signatures of correlated electrons and indications of ferromagnetic quantum criticality. In YbFe₂Al₁₀ localized f-electron spins of Yb become involved in correlations with a moderately enhanced electronic specific heat that classifies it as a non-ordered heavy-fermion compound.