Abstract
Muon spin relaxation (SR) and magnetic susceptibility measurements have been performed in the itinerant-electron magnet SrCaRuO, with 0.0, 0.3, 0.5, 0.65, 0.7, 0.75, 0.8, 0.9, and 1.0. SrRuO is a ferromagnet with the critical temperature K. Upon (Sr, Ca) substitution, decreases monotonically with increasing Ca concentration and the ferromagnetic order disappears around 0.7. Very weak static magnetism is observed in the 0.75 and 0.8 systems, while the 0.9 and 1.0 systems remain paramagnetic in their full volume. Phase separation between volumes with and without static magnetism was observed in the 0.65, 0.7, 0.75, and 0.8 systems, near the magnetic crossover around 0.7. In this concentration region, SR measurements revealed discontinuous evolution of magnetic properties in contrast to magnetization measurements, which exhibit seemingly continuous evolution. Unlike the volume-integrated magnetization measurements, SR can separate the effects of the ordered moment size and the volume fraction of magnetically ordered regions. The muon spin relaxation rate exhibits critical slowing down of spin fluctuations near in the ferromagnetic systems with 0.0–0.65, consistent with the behavior expected in the self-consistent renormalization theory of itinerant electron ferromagnets. The lack of maximum of in the 0.7 system indicates the disappearance of critical slowing down. These results demonstrate a first-order quantum evolution in the ferromagnet to paramagnet crossover near 0.7.
4 More- Received 4 February 2011
DOI:https://doi.org/10.1103/PhysRevB.84.224415
©2011 American Physical Society