Antiferromagnetic ordering in the doped Kondo insulator CeRhSb

Abstract

CeRhSb, the so-called ``Kondo insulator," is a mixed-valent compound showing a gap formation in the electronic density of states. On the other hand, CePdSb is ferromagnetically ordered with a Curie temperature of ~17 K. We have carried out magnetic susceptibility and electrical resistivity measurements on CeRh_1-xPd_xSb (0≤x≤1.0), to study the ground-state properties of this system. For small Pd doping in CeRhSb, up to 20%, the gap continually diminishes and no magnetic ordering is observed down to 2 K. In the region 0.3≤x≤0.4, as soon as the gap is suppressed, an antiferromagnetic ground state is observed. In the region 0.5≤x<0.7, the compounds are not single phase. At the CePdSb end, in the region 0.7≤x≤1, the ground state is ferromagnetic. The observation of an antiferromagnetic phase in the phase diagram of CeRh_1-xPd_xSb, where neither end is antiferromagnetic, is interesting and is discussed in the light of some recent theoretical models.