Muon spin relaxation and susceptibility measurements of an itinerant-electron system Sr 1 − x Ca x RuO 3 : Quantum evolution from ferromagnet to paramagnet

摘要: Muon spin relaxation ($\ensuremath{\mu}$SR) and magnetic susceptibility measurements have been performed in the itinerant-electron magnet Sr${}_{1\ensuremath{-}x}$Ca${}_{x}$RuO${}_{3}$, with $x=$ 0.0, 0.3, 0.5, 0.65, 0.7, 0.75, 0.8, 0.9, 1.0. SrRuO${}_{3}$ is a ferromagnet critical temperature ${T}_{c}\ensuremath{\sim}160$ K. Upon (Sr, Ca) substitution, ${T}_{c}$ decreases monotonically increasing Ca concentration $x$ ferromagnetic order disappears around 0.7. Very weak static magnetism observed 0.75 0.8 systems, while 0.9 1.0 systems remain paramagnetic their full volume. Phase separation between volumes without was near crossover In this region, $\ensuremath{\mu}$SR revealed discontinuous evolution of properties contrast to magnetization measurements, which exhibit seemingly continuous evolution. Unlike volume-integrated can separate effects ordered moment size volume fraction magnetically regions. The muon rate $1/{T}_{1}$ exhibits slowing down fluctuations 0.0--0.65, consistent behavior expected self-consistent renormalization theory itinerant electron ferromagnets. lack maximum 0.7 system indicates disappearance down. These results demonstrate first-order quantum paramagnet