The Crystal Electric Field Effect in the Distorted Kagome Lattice Ferromagnet Nd₃Ru₄Al₁₂

The distorted kagome lattice compound Nd₃Ru₄Al₁₂ shows a ferromagnetic phase transition at T_C =39 K. Reduced Nd magnetic moments with two different values of 2.66 and 0.95 µ_B are aligned along the c-axis below T_C. It was previously reported that a crystal electric field (CEF) effect may affect the reduced magnetic moments. To clarify the 4f -electronic state in Nd₃Ru₄Al₁₂, we performed CEF analyses for the inverse magnetic susceptibility and magnetization. We proposed the CEF level scheme of which the inverse magnetic susceptibilities along both a- and c-axes are reproduced. The ferromagnetic phase transition at T_C along the c-axis can be explained by a simple CEF model. In contrast, reduced magnetic moments cannot be understood by the simple CEF model, because calculated magnetization curves are quite larger than the experimental data.