Eu₃Ir₂In₁₅: a mixed-valent and vacancy-filled variant of the Sc₅Co₄Si₁₀ structure type with anomalous magnetic properties

Abstract

A new compound, Eu₃Ir₂In₁₅, has been synthesized using indium as an active metal flux. The compound crystallizes in the tetragonalP4/mbmspace group with lattice parametersa= 14.8580(4) Å,b= 14.8580(4)Å, andc= 4.3901(2)Å. It was further characterized by SEM-EDX studies. The effective magnetic moment (μ_eff) of this compound is 7.35 μ_B/Eu ion with a paramagnetic Curie temperature (θ_p) of -28 K, suggesting antiferromagnetic interaction. The mixed-valent nature of Eu observed in magnetic measurements was confirmed by XANES measurements. The compound undergoes demagnetization at a low magnetic field (10 Oe), which is quite unusual for Eu-based intermetallic compounds. Temperature-dependent resistivity studies reveal that the compound is metallic in nature. A comparative study was made between Eu₃Ir₂In₁₅and hypothetical vacancy-variant Eu₅Ir₄In₁₀, which also crystallizes in the same crystal structure. However, our computational studies along with control experiments suggest that the latter is thermodynamically less feasible compared to the former, and hence we propose that it is highly unlikely that an RE₅T₄X₁₀would exist with X as a group 13 element.