Physical properties of EuPd2As2 single crystals.

The physical properties of self-flux grown EuPd2As2 single crystals have been investigated by means of magnetization M, magnetic susceptibility χ, specific heat Cp, and electrical resistivity ρ measurements versus temperature T and magnetic field H. The crystal structure was determined using powder x-ray diffraction measurements, which confirmed the ThCr2Si2-type body-centered tetragonal structure (space group I4/mmm) reported previously. The ρ(T) data indicate that EuPd2As2 is metallic. The χ(T) data indicate that the Eu(+2) moments have spin S = 7/2 with g = 2. Long-range antiferromagnetic (AFM) ordering is apparent from the χ(T), Cp(T), and ρ(T) measurements. For H∥c the χ(T) indicates two transitions at TN1 = 11.0 K and TN2 = 5.5 K, whereas for H⊥c only one transition is observed at TN1 = 11.0 K. Between TN1 and TN2 the anisotropic χ(T) data suggest a planar noncollinear AFM structure, whereas at T < TN2 the χ(T) and M(H, T) data suggest a spin reorientation transition in which equal numbers of spins cant in opposite directions out of the ab plane. We estimate the critical field at 2 K at which all Eu moments become aligned with the field to be about 22 T. An upturn in ρ at T < TN1 suggests superzone energy gap formation below TN1. This behavior of ρ(T < TN1) is not sensitive to applied magnetic fields up to H = 12 T.