Low-temperature and high-pressure µSR study of the strongly correlatedCeNiSnHxcompounds

International audienceHydrogen insertion in the CeNiSn Kondo semiconductor induces antiferromagnetic ordering for CeNiSnH below TN=4.5K whereas CeNiSnH1.8 orders ferromagnetically below TC=7.0K. We present a detailed investigation of these CeNiSnHx 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., dTCdp=−0.17Kkbar−1 for CeNiSnH1.8 and dTNdp=0.016Kkbar−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 CeNiSnH1.8 are on different sides of Doniach's dome. The behavior of the CeNiSnH1.8 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 CeNiSnH1.8