Change of magnetic ground state by light electron doping in CeOs2Al10

Abstract

The effect of Ir substitution for Os in CeOs${}_{2}$Al${}_{10}$, with an unusually high N\'eel temperature of ${T}^{*}\ensuremath{\sim}28.5$ K, has been studied by high-resolution neutron diffraction and magnetization measurements. A small amount of Ir ($\ensuremath{\sim}$$8%$) results in a pronounced change of the magnetic structure of the Ce sublattice. The induced magnetic ground state is controlled by single ion anisotropy and implies an antiferromagnetic arrangement of the Ce moments along the $a$ axis, as expected from the anisotropy of the paramagnetic susceptibility. The value of the ordered moments, 0.92(1)${\ensuremath{\mu}}_{B}$, is substantially bigger than in the undoped compound, whereas the transition temperature is reduced down to 21 K. A comparison of the observed phenomena with the recently studied CeRu${}_{1.9}$Rh${}_{0.1}$Al${}_{10}$ system, exhibiting similar behavior [Kondo et al., J. Phys. Soc. Jpn. 82, 054709 (2013)], strongly suggests the electron doping as the main origin of the ground state changes. This provides additional ways for exploring the anomalous magnetic properties of the Ce(Ru/Os)${}_{2}$Al${}_{10}$ compounds.