Specific-heat study of Ce(Cu,Al)4 compounds

The CeCuxAl4−x compounds crystallize in the tetragonal BaNiSn3-type structure for x between 0.7 and 1.1. The unit cell volume as well as the c/a ratio decreases with increasing x. All compounds order magnetically with the ordering temperature decreasing with increasing the Cu content x. The specific heat in the ordered state follows the same type of behavior for all concentrations, suggesting similar type of magnons. The change of the specific heat in applied magnetic field, on the other hand, indicates transition between antiferromagnetic order in CeCuAl3 to ferromagnetic order in CeCu0.75Al3.25. The magnetic entropy at the ordering temperature is reduced below R ln 2 due to the Kondo effect. Specific heat of corresponding LaCuxAl4−x compounds was measured to analyze properly the magnetic specific heat in the paramagnetic region. The crystal field energy schemes were estimated and compared with neutron scattering data.