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Komiya, Seiki; Ando, Yoichi; Sun, Xiaofeng; Лавров, А. Н.

doi:10.1103/physrevb.65.214535

Cited by 102 publications

(62 citation statements)

References 45 publications

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“…The LSCO single crystals were grown by a traveling-solvent floating zone (TSFZ) technique (31). La 2 O 3 , SrCO 3 , and CuO powders were mixed with the cation ratio of La∶Sr∶Cu ¼ ð2 − xÞ∶x∶1.02 for each x and calcined at 780°C for 12 h, and then reground and calcined at 920°C for 12 h three times.…”

Section: Methodsmentioning

confidence: 99%

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Sonier

Kaiser

Pacradouni

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The doping of charge carriers into the CuO 2 planes of copper oxide Mott insulators causes a gradual destruction of antiferromagnetism and the emergence of high-temperature superconductivity. Optimal superconductivity is achieved at a doping concentration p beyond which further increases in doping cause a weakening and eventual disappearance of superconductivity. A potential explanation for this demise is that ferromagnetic fluctuations compete with superconductivity in the overdoped regime. In this case, a ferromagnetic phase at very low temperatures is predicted to exist beyond the doping concentration at which superconductivity disappears. Here we report on a direct examination of this scenario in overdoped La 2−x Sr x CuO 4 using the technique of muon spin relaxation. We detect the onset of static magnetic moments of electronic origin at low temperature in the heavily overdoped nonsuperconducting region. However, the magnetism does not exist in a commensurate long-range ordered state. Instead it appears as a dilute concentration of static magnetic moments. This finding places severe restrictions on the form of ferromagnetism that may exist in the overdoped regime. Although an extrinsic impurity cannot be absolutely ruled out as the source of the magnetism that does occur, the results presented here lend support to electronic band calculations that predict the occurrence of weak localized ferromagnetism at high doping.A ttempts within the framework of standard theories have failed to explain how high-temperature superconductivity emerges from charge carrier doping of an antiferromagnetic (AF) Mott insulator (1). The conventional Bardeen-CooperSchrieffer (BCS) theory of low-temperature superconductors (2) assumes that above the critical transition temperature (T c ) the electrons form a Landau Fermi liquid, and that superconductivity arises from pair condensation of the associated low-energy excitations (quasiparticles). What is clear in the case of copper oxides is that over the initial doping range where superconductivity first appears, ordinary Landau Fermi liquid theory does not apply. This realization has prompted theories in which the properties of the ordinary Fermi liquid are hidden (3), or alternatively only some properties of the Fermi liquid persist (4).A BCS-type theory may be applicable in the heavily overdoped region, where an ordinary Fermi liquid is observed (5-7). However, the recent proposal by Kopp et al. (8) that ferromagnetic (FM) fluctuations compete with d-wave superconductivity is a challenge to the notion that overdoped copper oxides strictly conform to such conventional wisdom. The primary motivation for their hypothesis is a strong upturn in the magnetic susceptibility immediately above T c for doping levels greater than p ∼ 0.19 (9-14). A tendency toward FM order for high charge doping (Fig. 1) is supported by electronic band calculations for super cells of La 2−x Ba x CuO 4 (15). However, these calculations favor the appearance of weak ferromagnetism about concentrated regions of ...

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Section: Methodsmentioning

confidence: 99%

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Sonier

Kaiser

Pacradouni

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…25 After the crystallographic axes are determined by using the X-ray Laue analysis, the crystals are cut into rectangular thin platelets with the typical sizes of 2.5 × 0.5 × 0.15 mm 3 , where the c axis is perpendicular or parallel to the platelet with an accuracy of 1 • . La 2−y Eu y CuO 4 samples are annealed in flowing pure He gas to remove the excess oxygen.…”

Section: Methodsmentioning

confidence: 99%

Heat transport ofLa2−yEuyCuO

2003

Self Cite

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To study the rare-earth doping effect on the phonon heat transport of La-based cuprates and shed light on the mechanism of phonon scattering, both ab-plane and c-axis thermal conductivities (κ ab and κc) are measured for La2−yEuyCuO4 (y = 0, 0.02 and 0.2) and La1.88−yEuySr0.12CuO4 (y = 0 and 0.2) single crystals. It is found that the phonon peak (at 20 -25 K) in κ ab (T ) of La2−yEuyCuO4 shows an anomalous Eu-doping dependence: it completely disappears for y = 0.02, which is discussed to be due to the local lattice distortions around Eu dopants, and reappears for y = 0.2 with much smaller peak magnitude compared to y = 0 sample. In contrast to the strong suppression of the phonon peak in Eu-doped La2CuO4, Eu-doping to La1.88Sr0.12CuO4 enhances the low-T phonon heat transport that results in the reappearance of the phonon peak in this chargecarrier-doped system. The data clearly show that the establishment of static stripe phase rather than the structural change is responsible for the reappearance of phonon peak.

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“…In this way the La 2 CuO 4+δ differs drastically from Sr doped system, where the holes remain quasi two-dimensional. Really, the ratio σ ab /σ c in lightly doped La 1−x Sr x CuO 4 crystals of good quality can be as high as several thousands [27].…”

Section: Introductionmentioning

confidence: 99%

Magnetoresistive study of the antiferromagnetic–weak ferromagnetic transition in single-crystal La2CuO4+δ

Белевцев

Далакова

Savitsky

et al. 2004

Low Temperature Physics

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The resistive measurements were made to study the magnetic field-induced antiferromagnetic (AF) -weak ferromagnetic (WF) transition in La2CuO4 single-crystal. The magnetic field (DC or pulsed) was applied normally to the CuO2 layers. The transition manifested itself in a drastic decrease of the resistance in critical fields of 5-7 T. The study is the first to display the effect of the AF -WF transition on the conductivity of the La2CuO4 single-crystal in the parallel -to -CuO2 layers direction. The results provide support for the 3-dimensional nature of the hopping conduction of this layered oxide.

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c-axis transport and resistivity anisotropy of lightly to moderately dopedLa2−xSr

Cited by 102 publications

References 45 publications

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Direct search for a ferromagnetic phase in a heavily overdoped nonsuperconducting copper oxide

Heat transport ofLa2−yEuyCuO

Magnetoresistive study of the antiferromagnetic–weak ferromagnetic transition in single-crystal La2CuO4+δ

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