Tuning the ferromagnetic phase in the CDW compound SmNiC(2) via chemical alloying

We report a study on tuning the charge density wave (CDW) ferromagnet SmNiC(2) to a weakly coupled superconductor by substituting La for Sm. X-ray diffraction measurements show that the doped compounds obey Vegard’s law, where La (Lu) alloying expands (shrinks) the lattice due to its larger (smaller) atomic size than Sm. In the series Sm(1−x)La(x)NiC(2), CDW transition (T(CDW) = 148 K) for SmNiC(2) is gradually suppressed, while the ferromagnetic (FM) ordering temperature (T(C)) at 17 K slightly increases up to x = 0.3. For x > 0.3, T(C) starts to decrease and there is no signature that could be related with the CDW phase. Electrical resistivity, magnetic susceptibility and specific heat measurements point toward the possible presence of a FM quantum critical point (QCP) near x = 0.92, where the T(C) is extrapolated to zero temperature. Superconductivity in LaNiC(2) (T(sc) = 2.9 K) is completely suppressed with small amount of Sm inclusion near the proposed FM critical point, indicating a competition between the two ordered phases. The tunable lattice parameters via chemical substitution (La,Lu) and the ensuing change among the ordered phases of ferromagnetism, CDW and superconductivity underscores that SmNiC(2) provides a rich avenue to study the rare example of a FM QCP, where the broken symmetries are intricately correlated.