Electronic and magnetic properties of EuNi2−δSb2 structural variants

Abstract

X-ray diffraction, magnetic susceptibility, magnetization, heat capacity and electrical resistivity results are reported for single crystals of two structural variants of EuNi2−δSb2 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 TN1 = 6.9 K and then undergoes a first order phase transition at TM = 4.6 K. The ThCr2Si2-variant exhibits simpler behavior, with antiferromagnetic ordering at TN2 = 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−δSb2 emerges as a useful system in which to study the impact of structural variation on magnetism in a Eu-based metal.