Evolution of ferromagnetic and non-Fermi-liquid states with doping; The case of Ru-doped UCoGe

Ruドーピングによって生じるUCoGe強磁性、非フェルミ液体状態

Valika, M.*; Pospisil, J.; Divi, M.*; Prokleka, J.*; Sechovsk, V.*; Abd-Elmeguid, M. M.*

Valika, M.*; Pospisil, J.; Divi, M.*; Prokleka, J.*; Sechovsk, V.*; Abd-Elmeguid, M. M.*

We have investigated the impact of Ru substitution for Co on the behavior of the ferromagnetic superconductor UCoGe by performing X-ray diffraction, magnetization, specific heat, and electrical resistivity measurements on polycrystalline samples of the UCoRuGe series (0 x 0.9). The initial Ru substitution up to x = 0.1 leads to a simultaneous sharp increase of the Curie temperature and spontaneous magnetization up to maximum values of TC = 8.6 K and MS = 0.1mB per formula unit, respectively, whereas superconductivity vanishes already for x = 0.03. Further increase of the Ru content beyond x = 0.1 leads to a precipitous decrease of both TC and MS towards a ferromagnetic quantum critical point (QCP) at xcr = 0.31. We discuss the evolution of ferromagnetism with x on the basis of band structure changes due to varying 5f -ligand hybridization.