Effect of H insertion on the magnetic, electronic, and structural properties of CeCoSi

Contrary to other cerium equiatomic intermetallic systems (CeTX with T=transition metal, X=p metal) which become magnetically ordered upon hydrogen insertion, magnetic measurements characterize an antiferromagnet for CeCoSi and a spin fluctuation system for its hydride CeCoSiH. The presented results of electrical and magnetic properties of the silicide CeCoSi demonstrate the existence of an antiferromagnetic transition at T-N=8.8(2) K. For the purpose of further assessing the experimental findings, the electronic and magnetic sructures of CeCoSi and CeCoSiH are self-consistently calculated within the local spin density functional LSDF theory. The analysis of the electronic structures and of the chemical bonding properties lead to suggest that the chemical effect of hydrogen prevails over the cell expansion effect which would enhance the magnetization otherwise. Spin orbit coupling effects on cerium are examined. A potential antiferromagnetic structure with a propagation along the c axis is proposed for CeCoSi ground state.