ABSTRACT
Rare earth-metalloid compounds display various types of magnetic ordering and magnetic transitions. The most interesting compounds among this group of magnetic materials are the silicides and geramanides. In particular, RMn2Ge2 (R¼La, Gd, Tb, Dy) compounds have layered crystal structure, two magnetic sublattices (Mn and R) ordering at different temperatures and strong dependence of exchange interactions on interatomic distance. All these factors determine complex magnetic structures of the compounds with multiple magnetic phase transitions, including first-order transitions. In recent years attention of investigators was attracted to the system (RR0)5(Si-Ge)4. This is related to unusual magnetic properties discovered in Gd5(Si-Ge)4 compounds. In a certain concentration range in this system the compounds undergo magnetic first-order transition accompanied by reversible structural transition and essential change in lattice parameters and magnetic properties. This effect causes high magnetocaloric properties of Gd5(Si-Ge)4 and increased interest for these compounds.
