Hydrogen insertion in the CeNiSn Kondo semiconductor induces antiferromagnetic ordering for CeNiSnH below $T_N=4.5\mathrm{K}$ whereas $\mathrm{CeNiSn}{\mathrm{H}}_{1.8}$ orders ferromagnetically below $T_C=7.0\mathrm{K}$. We present a detailed investigation of these $\mathrm{CeNiSn}{\mathrm{H}}_x$ compounds by means of muon spin spectroscopy performed at both ambient and high pressure (up to 23 kbar). It is shown that both magnetic ordering temperatures are sensitive to the applied pressure but in opposite directions, i.e., $\frac{d{T}_C}{dp}=-0.17\mathrm{K}\mathrm{kba}{\mathrm{r}}^{-1}$ for $\mathrm{CeNiSn}{\mathrm{H}}_{1.8}$ and $\frac{d{T}_N}{dp}=0.016\mathrm{K}\mathrm{kba}{\mathrm{r}}^{-1}$ for CeNiSnH, respectively. This difference is discussed in terms of hydrogen-induced modification of the balance between the Ruderman-Kittel-Kasuya-Yosida (RKKY) and the Kondo interactions. The µSR study demonstrates that the CeNiSnH and $\mathrm{CeNiSn}{\mathrm{H}}_{1.8}$ are on different sides of Doniach's dome. The behavior of the $\mathrm{CeNiSn}{\mathrm{H}}_{1.8}$ is interpreted as resulting from an increase of the hybridization between $4f$ and $5d$ states and a concomitant steep increase of the Kondo temperature upon applying pressure. In the quest for a quantum critical point, an estimated pressure of about 35 kbar is expected to suppress the magnetism in $\mathrm{CeNiSn}{\mathrm{H}}_{1.8}$.

• Received 14 March 2016
• Revised 3 May 2016

DOI:https://doi.org/10.1103/PhysRevB.93.224424