High pressure study of the interplay between charge and magnetic ortdering in SmNiC2

Charge density wave (CDW) ordering in SmNiC2 is followed at lower temperatures by the ferromagnetic (FM) ordering of the Sm moments. Below the FM onset, the CDW order is fully suppressed, evidencing a strong interplay between the two types of ordering. The CDW suppression was attributed to the weakening of the Fermi surface nesting conditions, which are relevant to the formation of the CDW, in the FM state. In contrast, ab initio calculations indicate that hydrostatic pressure (HP) improves the nesting conditions and therefore favours the CDW formation. HP electrical resistivity experiments showed that the CDW onset increases under HP, while parallely the FM transition temperature decreases, and suggested the presence of a hidden FM quantum critical point. Here we will explore directly the pressure evolution of charge ordering and its interplay with magnetism in this system, while monitoring its crystal structure, through a HP x-ray diffraction study of SmNiC2 single crystals.