Specific heat studies of RCu2Si2 (R=Tb, Ho) and RCu2Ge2 (R=Gd, Tb) compounds

Magnetic properties of RCu2Si2 (R=Tb, Ho) and RCu2Ge2 (R=Gd, Tb), crystallizing with the tetragonal ThCr2Si2-type crystal structure, were investigated by means of magnetic and calorimetric measurements. All compounds exhibit antiferromagnetic ordering below T N equal to 11.2 K for TbCu2Si2, 5.3 K for HoCu2Si2, 12.0 K for GdCu2Ge2 and 12.5 K for TbCu2Ge2. At temperatures of T t = 8.5 K for TbCu2Si2 and 9.8 K for TbCu2Ge2 additional phase transitions were observed. Apart from the investigation on magnetic phase transitions, magnetic contributions to the specific heat were analyzed in terms of Schottky effect. The corresponding crystal electric field (CEF) level splitting schemes were calculated. Moreover, the phononic characteristic temperatures were estimated.