RESUMO
X-ray diffraction, magnetic susceptibility, magnetization, heat capacity and electrical resistivity results are reported for single crystals of two structural variants of EuNi2-δ Sb2 that crystallize in the CaBe2Ge2 and ThCr2Si2-type structures. While the former occurs with a stoichiometric ratio, the latter exhibits a Ni site vacancy (δ = 0.36). Both systems exhibit similar magnetic behavior at elevated temperatures, where there is an isotropic Curie-Weiss temperature dependence that indicates an antiferromagnetic exchange interaction between divalent europium ions, although it is stronger for the CaBe2Ge2-variant. At low temperatures, the differing structural environments that surround the Eu ions result in distinct ordering behavior. The CaBe2Ge2-variant orders antiferromagnetically near T N1 = 6.9 K and then undergoes a first order phase transition at T M = 4.6 K. The ThCr2Si2-variant exhibits simpler behavior, with antiferromagnetic ordering at T N2 = 5.6 K. For both compounds, an applied magnetic field suppresses the ordering temperatures and induce metamagnetic phase transitions, while applied pressure causes the ordering temperatures to increase. From these results, EuNi2-δ Sb2 emerges as a useful system in which to study the impact of structural variation on magnetism in a Eu-based metal.
