Ferromagnetic Fluctuations in the Heavily Overdoped Regime of Single-Layer High- Cuprate Superconductors.

To investigate proposed ferromagnetic fluctuations in the so-called single-layer Bi-2201 and La-214 high- cuprates, we performed magnetization and electrical resistivity measurements using single-layer Tl-2201 cuprates TlBaCuO and La-214 LaSrCuO in the heavily overdoped regime. Magnetization of TlBaCuO and LaSrCuO exhibited the tendency to be saturated in high magnetic fields at low temperatures, suggesting the precursor behavior toward the formation of a ferromagnetic order. It was found that the power of temperature obtained from the temperature dependence of the electrical resistivity is ~4/3 and ~5/3 for Bi-2201 and LaSrCuO, respectively, and is ~4/3 at high temperatures and ~5/3 at low temperatures in TlBaCuO.

Fabrication of High-Temperature Quasi-Two-Dimensional Superconductors at the Interface of a Ferroelectric Ba_{0.8}Sr_{0.2}TiO_{3} Film and an Insulating Parent Compound of La_{2}CuO_{4}.

We report the first observation of superconductivity in a heterostructure consisting of an insulating ferroelectric film (Ba_{0.8}Sr_{0.2}TiO_{3}) grown on an insulating parent compound of La_{2}CuO_{4} with [001] orientation.

Development of Ferromagnetic Fluctuations in Heavily Overdoped (Bi,Pb)_{2}Sr_{2}CuO_{6+δ} Copper Oxides.

We demonstrate the presence of ferromagnetic (FM) fluctuations in the superconducting and nonsuperconducting heavily overdoped regimes of high-temperature superconducting copper oxides, using (Bi,Pb)_{2}Sr_{2}CuO_{6+δ} (Bi-2201) single crystals. Magnetization curves exhibit a tendency to be saturated in high magnetic fields at low temperatures in the heavily overdoped crystals, which is probably a precursor phenomenon of a FM transition at a lower temperature. Muon spin relaxation detects the enhancement of spin fluctuations at high temperatures below 200 K.