Competing magnetic order in EuPd₃Si₂

Single crystals of EuPd3Si2 were grown using a high-temperature EuPd-flux method. The material was structurally and chemically characterized by single-crystal x-ray diffraction, powder x-ray diffraction, Laue method and energy-dispersive x-ray spectroscopy. The structural analysis confirmed the orthorhombic crystal structure (space group Imma) but revealed differences in the lattice parameters and bond distances. The composition is close to the ideal 1:3:2 stoichiometry with an occupation of 7 % of the Si sites by Pd. The heat capacity, electrical resistivity, and magnetic susceptibility show two magnetic transitions indicating magnetic ordering below TN1 = 61 K and a spin reorientation at TN2 = 40 K. The orthorhombic material shows magnetic anisotropy, with anisotropy constants K₁ = 7.1 × 10⁵ J/m³ and K₂ = 4.2 × 10⁵ J/m³, for field applied along the three main symmetry axes, which is summarized in the temperature-field phase diagrams. The susceptibility data hint to an alignment of the magnetic moments along [100] between TN1 and TN2. Below TN2 the magnetic structure changes to an arrangement with moments canted away from [100]. The single crystals investigated in this study are suggested to show antiferromagnetic (AFM) order below TN1 instead of ferromagnetism that sets in at higher TC1 = 78 K which might originate from certain differences in the structure, composition or defects that have an impact on the dominant coupling constants of the RKKY interaction.