Mass enhancement of nearly trivalent compound EuCo₂Si₂: Studied by the de Haas-van Alphen experiments and energy band calculations

We succeeded in growing single crystals of EuCo₂Si₂ by the Bridgman method, and carried out the de Haas-van Alphen (dHvA) experiments. EuCo₂Si₂ was previously studied from a viewpoint of the trivalent electronic state on the basis of the magnetic susceptibility and X-ray absorption experiments, whereas most of the other Eu compounds order magnetically, with the divalent electronic state. The detected dHvA branches in the present experiments are found to be explained by the results of the full potential linearized augmented plane wave energy band calculations on the basis of a local density approximation (LDA) for YCo₂Si₂ (LDA) and EuCo₂Si₂ (LDA + U), revealing the trivalent electronic state. The detected cyclotron effective masses are moderately large, ranging from 1.2 to 2.9 m₀.