Structural and magnetic properties of stage-2 EuCl3-graphite intercalation compound

Structural and magnetic properties of stage-2 EuCl3-graphite intercalation compounds have been studied by using x-ray diffraction, electron diffraction, and dc magnetic susceptibility. The repeat distance along the c axis is 13.280.02. The EuCl3 intercalate layer forms a three-layer sandwich of Cl-Eu-Cl, where the distance between Eu and Cl layers is 1.67. The layer structure of the EuCl3 intercalate layer is similar to that of YCl3 type. The EuCl3 layer is hexagonal with two Eu ions per unit cell (lattice constant 7.38) and consists of domain structures generated by the rotation of the (3×3) commensurate structure with respect to the graphite lattice by 6.3°, 10°, 13.8°, and 17.5°. The EuCl3 layer is modulated by the graphite layer. The dc magnetic susceptibility is found to be a sum of contributions from Eu2+ and Eu3+ ions. The concentrations of Eu3+ and Eu2+ in the EuCl3 intercalate layer are 0.994 and 0.006, respectively. The susceptibility contribution from Eu2+ ions obeys the Curie-Weiss law with a Curie-Weiss temperature FTHETA=10.11.1 K. The susceptibility contribution from the van Vleck ion Eu3+ is almost independent of temperature, where the energy difference between 7F0 and 7F1 levels is given by E1=538 K.