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Synthesis, Structure, and Complex Magnetism of MIr2In8 (M = Eu, Sr)
journal contribution
posted on 2016-03-07, 20:43 authored by Nicholas
P. Calta, Sergey L. Bud’ko, Alexandra P. Rodriguez, Fei Han, Duck Young Chung, Mercouri G. KanatzidisWe report the synthesis, crystal
structure, and physical properties of two new polar intermetallic
compounds, EuIr2In8 and SrIr2In8. Both were synthesized in good yield using In metal as a
reactive flux medium, enabling the growth of large crystals for physical
property measurements. They crystallize in the orthorhombic space
group Pbam with the CeFe2Al8 structure type, which is sometimes also referred to as the CaCo2Al8 structure type. The two analogues have unit
cell parameters of a = 13.847(3) Å, b = 16.118(3) Å, and c = 4.3885(9)
Å for M = Eu and a = 13.847(3) Å, b = 16.113(3) Å, and c = 4.3962(9)
Å for M = Sr at room temperature. SrIr2In8 is a diamagnetic metal with no local magnetic moments on either
the Sr or Ir sites, and the diamagnetic contribution from core electrons
overwhelms the expected Pauli paramagnetism normally seen in intermetallic
compounds. Magnetism in EuIr2In8 is dominated
by the local Eu moments, which order antiferromagnetically at 5 K
in low applied fields. Increasing the field strength depresses the
magnetic ordering temperature and also induces a spin reorientation
at lower temperature, indicating complex competing magnetic interactions.
Low-temperature heat capacity measurements show a significant enhancement
of the Sommerfeld coefficient in EuIr2In8 relative
to that in SrIr2In8, with estimated values of
γ = 118(3) and 18.0(2) mJ mol–1 K–2, respectively.