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

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Anisotropic magnetic properties of single crystalline RAu₂Ge₂ (R = La, Ce and Pr) compounds are reported. LaAu₂Ge₂ exhibit a Pauli-paramagnetic behavior whereas CeAu₂Ge₂ and PrAu₂Ge₂ show an antiferromagnetic ordering with Neel temperatures Tₙ = 13.5 and 9 K, respectively. The anisotropic magnetic response of Ce and Pr compounds establishes [001] as the easy axis of magnetization and a sharp spin-flip type metamagnetic transition is observed in the magnetic isotherms. The resistance and magnetoresistance behavior 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.