Effects of Ga and Si Substitutions for Al in CeRu₂Al₁₀ on the Unusual Antiferromagnetic Order in the Kondo Semiconducting State

Abstract

We have studied the effects of Ga and Si substitutions on the antiferromagnetic (AF) Kondo semiconductor CeRu 2 Al 10 which orders at rather high temperature T N = 27 K. In CeRu 2 Al 10-x Ga x , the semiconducting behavior is suppressed with increasing x up to x = 0.8. Thereby, T N is suppressed down to 24.5 K. The Si substitution changes the AF state more strongly. In fact, T N decreases to 23 K for CeRu 2 Al 9.9 Si 0.1 , probably due to the doping of 3p electrons. The magnetic susceptibility along the orthorhombic a-axis exhibits a sharp peak at T N below which those along the b-and c-axes do not decrease. This change can be explained by the reorientation of the ordered moments from the c-axis in CeRu 2 Al 10 to the a-axis in CeRu 2 Al 9.9 Si 0.1 . These findings indicate the importance of electron density for the unusual AF order in CeRu 2 Al 10 .