The magnetic ground state of the Rh-doped Kondo semiconductor CeRu${}_2$Al${}_{10}$ [Ce(Ru${}_{1-x}$Rh${}_x$)${}_2$Al${}_{10}$] is investigated with the muon spin relaxation method. Muon spin precession with two frequencies is observed in the $x=0$ sample, while only one frequency is present in the $x=0.05$ and 0.10 samples, which is attributed to the broad static field distribution at the muon site. The internal field at the muon site is enhanced from about 180 G in the $x=0$ sample to about 800 G in the Rh-doped samples, supporting the spin-flop transition as suggested by the magnetization measurement, and the boundary of different magnetic ground states is identified around $x=0.03$. The drastic change of magnetic ground state by a small amount of Rh doping (3%) indicates that the magnetic structure in CeRu${}_2$Al${}_{10}$ is not robust and can be easily tuned by external perturbations such as electron doping. The anomalous temperature dependence of the internal field in CeRu${}_2$Al${}_{10}$ is suggested to be attributed to the hyperfine interaction between muons and conduction electrons.

• Received 22 July 2013

DOI:https://doi.org/10.1103/PhysRevB.88.115206