New orthorhombic derivative of CaCu<inf>5</inf>-type structure: RNi <inf>4</inf>Si compounds (R=Y, La, Ce, Sm, Gd-Ho), crystal structure and some magnetic properties

The crystal structure of new YNi4Si-type RNi4Si (R=Y, La, Ce, Sm, Gd-Ho) compounds has been established using powder X-ray diffraction. The YNi4Si structure is a new structure type, which is orthorhombic derivative of CaCu5-type structure (space group Cmmm N 65, oC12). GdNi4Si and DyNi4Si compounds order ferromagnetically at 25 and 19 K, respectively whereas YNi4Si shows antiferromagnetic nature. At 15 K, DyNi4Si shows second antiferromagnetic-like transition. The magnetic moment of GdNi4Si at 5 K in 50 kOe field is ~7.2 μB/f.u. suggesting a completely ordered ferromagnetic state. The magnetocaloric effect of GdNi4Si is calculated in terms of isothermal magnetic entropy change and it reaches the maximum value of -12.8 J/kg K for a field change of 50 kOe near TC ~25 K. © 2013 Elsevier Inc.