| Among heavy fermion materials, a relationship between unconventional superconductivity and magnetism has been observed. The dependence of the magnetic transitions of CexLa1-xRhyIr1-y In5 with respect to temperature and magnetic field applied along the tetragonal c and a crystal axes is examined using heat capacity measurements. The magnetic phase diagram of CeRh yIrl-yIn5 for the applied transitions in the a direction shows the magnetic structure of CeRhIn5 is unchanged by Ir doping. Doping of Ir in small concentrations is shown to increase the antiferromagnetic transition temperature TN. La doping or higher concentration of Ir is shown to lower TN. This shows the RKKY interaction, which leads to long range order in CeRhIn5, is of the same magnitude as the Kondo effect. The high temperature tail of the nuclear Schottky peak is seen in all of the data and can be accurately separated to identify the Ce f-electron contribution to the magnetic heat capacity. |
