Magnetocrystalline anisotropy in RAu2Ge2 (R = La, Ce and Pr) single crystals

Anisotropic magnetic properties of single crystalline RAu2Ge2 (R=La, Ce and Pr) compounds are reported. LaAu2Ge2 exhibits a Pauli-paramagnetic behaviour whereas CeAu2Ge2 and PrAu2Ge2 show an antiferromagnetic ordering with Nèel temperatures TN = 13.5 and 9 K, respectively. The anisotropic magnetic response of Ce and Pr compounds establishes [0 0 1] as the easy axis of magnetization and a sharp spin-flip type metamagnetic transition is observed in the magnetic isotherms with H // [0 0 1]. The transport and magnetotransport behaviour of these compounds, in particular LaAu2Ge2, indicate an anisotropic Fermi surface. The magnetoresistivity of CeAu2Ge2 apparently reveals the presence of a residual Kondo interaction. A crystal electric field analysis of the anisotropic susceptibility in conjunction with the experimentally inferred Schottky heat capacity enables us to propose a crystal electric field level scheme for Ce and Pr compounds. For CeAu2Ge2 our values are in excellent agreement with the previous reports on neutron diffraction. The heat capacity data in LaAu2Ge2 show clearly the existence of Einstein contribution to the heat capacity.