Controlling magnetism via transition metal exchange in the series of intermetallics Eu(T1,T2)5In (T = Cu, Ag, Au)

Abstract

Three series of intermetallic compounds Eu(T1,T2)₅In (T = Cu, Ag, Au) have been investigated over their full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single crystal X-ray diffraction revealing that the representatives fall into two structure types: CeCu₆ (oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) ų) and YbMo₂Al₄ (tI14, I4/mmm, a = 7.139(2)–7.199(2) Å, c = 5.417(3)–5.508(1) Å, V = 276.1(2)–285.8(1) ų). The structural preference was found to depend on the cation/anion size ratio, while the positional preference within the CeCu₆ type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution, appears to be the main driving force for the change of magnetic ordering. While EuAg₅In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au)₅In alloys with CeCu₆ structure show complex magnetic behaviors and a strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo₂Al₄ type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu_2.66Cu_2.34In reveals a double-peak structure evolving with the magnetic field. However, low-temperature X-ray powder diffraction does not show a structural transition.