Electoronic structure and Fermi surface of EuX_2(X=Rh, Ir)

We investigated the electronic structures of EuX_2 (X=Rh and Ir) by using the relativistic linear augmented-plane-wave (RLAPW) method with the exchange-correration potential in the local density approximation. All 4f electrons in Eu were assumed to be itinerant, which means that these 4f electrons are treated as valence electrons, and the calculation was performed in the paramagnetic phase. Note here that relativity should be taken into account, because of the large atomic numbers of the constituent atoms. We found that the energy bands near the Fermi level are mainly because of the hybridization between the Eu 4f and X d electrons. These compounds are compensated metals because of having two chemical units in the unit cell. The Fermi surface of EuRh_2 is found to consists of two hole sheets and two electron sheets. The Fermi surface produces many de Haas-van Alphen frequencies in the wide frequency range between 1 MOe and 300 MOe. In addition, we calculated LaRh_2 and LaIr_2 that have the same number of valence electrons of EuRh_2 and EuIr_2