Successive Magnetic Transitions Relating to Itinerant Spins and Localized Cu Spins in La_2−xSr_xCu_1−yFe_yO₄: Possible Existence of Stripe Correlations in the Overdoped Regime

Abstract

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 Fe 3+ spins due to the RKKY interaction based on itinerant spins at higher temperatures and a stripe-order transition of localized Cu 2+ spins at lower temperatures. The stripeorder 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 neutronscattering 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.

Fermi-liquid state in $T$*-type La$_{1-x/2}$Eu$_{1-x/2}$Sr$_x$CuO$_4$ revealed via element substitution effects on magnetism

“…The dashed line represents Tsg for overdoped La2−xSrxCu1−yFeyO4 with x = 0.20 + y taken from Ref. 39 B int below T m indicates the development of the moment size of the Cu spins in the ordered phase, although V m is almost 100 %. However, the significant damping of the spectra suggests a rather short-range magnetic order with a broad distribution of the internal magnetic fields at the muon stopping sites, even at low temperatures.…”

“…Electronic states in pristine cuprates have been studied intensively through impurity substitution effects on magnetic correlations [30][31][32][33][34][35][36][37][38][39][40] . In LESCO, nonmagnetic Zn (Zn 2+ , S = 0) substitution effectively enhances the magnetic order in the pristine sample with p 0.14, and induces weak static magnetism, even for p 0.14 [31][32][33] .…”

“…In contrast, the localized spins form a one-dimensional stripe-like domain in UD LSCO 35 . From these results, a doping-induced cross-over of the electronic state from the strongly correlated electronic state to the Fermi liquid (FL) state has been discussed 35,39 .…”

“…Following previous works [30][31][32][33][34][35][36][37][38][39][40] , we investigated the magnetism in Fe-substituted LESCO (Fe-LESCO) and Zn-substituted LESCO (Zn-LESCO) by µSR and magnetic susceptibility measurements. This paper is organized as follows.…”

Magnetic Impurity Effects on Ferromagnetic Fluctuations in Heavily Overdoped (Bi,Pb)$_2$Sr$_2$Cu$_{1-y}$Fe$_y$O$_{6+δ}$ Cuprates

“…20) The µSR and χ measurements in overdoped La 2−x Sr x Cu 1−y Fe y O 4 revealed the formation of a spin-glass state due to the RKKY interaction between Fe 3+ spins. 21) Hiraka et al suggested from elastic neutron-scattering experiments in Fe-substituted Bi 1.75 Pb 0.35 Sr 1.90 Cu 1−y Fe y O 6+δ that AF spin clusters are formed around Fe. 22) In non-SC HOD Bi-2201, our former µSR measurements revealed that the 5% Fe substitution for Cu enhanced the spin correlation and induced some forms of spin ordering at low temperatures, suggesting the development of ferromagnetic fluctuations owing to the Fe substitution.…”