New hydrides REScSiH and REScGeH (RE = La, Ce) : structure, magnetism, and chemical bonding

Bernard Chevalier (1) , Wilfried Hermes (2) , Birgit Heying (2) , Ute Ch. Rodewald (2) , Adrienne Hammerschmidt (2) , Samir F. Matar (1) , Etienne Gaudin (1) , Rainer Pöttgen (2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Institut für Anorganische und Analytische Chemie

The La₂Sb type silicides and germanides REScSi and REScGe (RE = La, Ce) were synthesized from the elements by arc-melting and subsequent annealing at 1170 K. The structures of LaScSi and LaScGe were refined on the basis of single-crystal X-ray diffraction data. The structures consist of a stacking of two-dimensional [ScSi] networks with ScSi_4/4 rectangles, which are separated by rare earth atoms, which leave RE_4/4 tetrahedral voids. The latter can be completely filled by hydrogenation leading to the quaternary hydrides REScSiH and REScGeH (RE = La, Ce). Hydrogenation is accompanied by an anisotropic unit cell expansion, i.e., a decrease in the a lattice parameter and a strong increase in c. The H-insertion into the compounds based on cerium induces for both a quasi-2D structure, a strong decrease of their antiferromagnetic ordering; for instance T_N decreases from 26 to 3.0 K in the sequence CeScSi → CeScSiH and the occurrence of the influence of the Kondo effect evidenced by electrical resistivity and specific heat measurements. The electronic structure calculation applied to CeScSi and its hydride reveals strong Ce−H bonding influencing the magnetic properties of CeScSiH.

Domaines: Matériaux

Bernard Chevalier, Wilfried Hermes, Birgit Heying, Ute Ch. Rodewald, Adrienne Hammerschmidt, et al.. New hydrides REScSiH and REScGeH (RE = La, Ce) : structure, magnetism, and chemical bonding. Chemistry of Materials, 2010, 22 (17), pp.5013-5021. ⟨10.1021/cm101290f⟩. ⟨hal-00528356⟩