  In order to investigate the relationship between the so-called stripe
correlations and the high-Tc superconductivity, we have carried out magnetic
susceptibility and zero-field muon-spin-relaxation measurements in partially
Fe-substituted La2-xSrxCu1-yFeyO4 (LSCFO). It has been found that the Fe
substitution induces successive magnetic transitions in the overdoped regime,
namely, a spin-glass transition of Fe3+ spins due to the RKKY interaction based
on itinerant spins at higher temperatures and a stripe-order transition of
localized Cu2+ spins at lower temperatures. The stripe-order transition
disappears at the hole concentration of ~0.28 per Cu which coincides with the
endpoint of the superconductivity in pristine La2-xSrxCuO4, suggesting that the
stripe correlations are closely related to the high-Tc superconductivity in the
overdoped regime as well as in the underdoped regime. As for the spin-glass
state, it has been found that the contribution of polarized itinerant spins to
the muon-spin depolarization is not negligible. Taking into account
neutron-scattering results by R.-H. He et al. [Phys. Rev. Lett. 107, 127002
(2011)] that a spin-density-wave (SDW) order has been observed in overdoped
LSCFO, the present results demonstrate the presence of a novel coexistent state
of a SDW order and a spin-glass state.
