Magnetic Properties of Incommensurate Layer Compounds, (CeS)1.2NbS₂and (CeS)0.6NbS₂

The magnetic susceptibilities and magnetizations of incommensurate layer compounds (CeS) 1.2 NbS 2 and (CeS) 0.6 NbS 2 are reported. The magnetic susceptibilities in the paramagnetic region of the above two compounds are analyzed taking account of the crystal field acting on Ce 3+ and the molecular field. The crystal field splitting of 2 F 5/2 multiplet (Ce 3+ ) is estimated at ca. 500 K. The large splitting suggests that the screening of the crystal field by conduction electrons is weak in the CeS layer. The compound (CeS) 1.2 NbS 2 orders antiferromagnetically near 3 K accompanied by a weak-ferromagnetic moment, while a magnetic ordering with a spontaneous magnetization is observed near 3 K in (CeS) 0.6 NbS 2 . Both the two compounds display a metamagnetic transition at 2.3 kOe ( T =2.0 K). Possible magnetic structures are discussed in terms of ferromagnetic CeS layers.