Eu3Ir2In15: A Mixed-Valent and Vacancy-Filled Variant of the Sc5Co4Si10 Structure Type with Anomalous Magnetic Properties

A new compound, Eu3Ir2In15, has been synthesized using indium as an active metal flux. The compound crystallizes in the tetragonal P4/mbm space group with lattice parameters a = 14.8580(4) angstrom, b = 14.8580(4) angstrom, and c = 4.3901(2) angstrom. It was further characterized by SEM-EDX studies. The effective magnetic moment (mu(eff)) of this compound is 7.35 mu(B)/Eu ion with a paramagnetic Curie temperature (theta(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 Eu3Ir2In15 and 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 RE5T4X10 would exist with X as a group 13 element.