Electronic properties and crystal structures of RE3Rh2Ga2 and RE3Rh3Si2 (RE = La, Ce)

Polycrystalline samples of Ce3Rh2Ga2, Ce3Rh3Si2 and their La-based isostructural analogues were studied by means of magnetic susceptibility, magnetization and electrical resistivity measurements. The crystal structure of La3Rh3Si2 (Ce3Rh3Si2 type) was investigated by single-crystal X-ray diffraction. The cerium gallide was found to order ferromagnetically at TC = 3.5 K, whereas for the silicide more complex magnetic behaviour was established with antiferromagnetic order setting at TN = 6.5 K and subsequent change in the magnetic structure occurring at Tt = 5.5 K. Both cerium compounds exhibit weak Kondo effect. The LIII-edge XAS data indicated rather stable 4f1 character of cerium in both compounds. The electronic band structures of Ce3Rh2Ga2 and Ce3Rh3Si2 were calculated by the LMTO method and compared with those of Ce3Rh2Ge2 and La3Rh2Ge2. For each Ce-based compound the total electronic DOS is dominated by a peak of Ce 4f states near the Fermi level and a Rh 4d band located about 2 eV below the Fermi energy.