Possible ferromagnetic phase in non-superconducting heavily overdoped cuprates of Bi-2201

In order to investigate the possible ferromagnetic phase in the non-superconducting (non-SC) heavily overdoped (HOD) regime of high-T_c cuprates suggested by Sonier et al. [Proc. Natl. Acad. Sci. USA 107, 17131 (2010)] in La_2-xSr_xCuO₄, both the magnetization and in-plane electrical resistivity, ρ_ab, have been measured using single crystals of Bi_1.76Pb_0.35Sr_1.89CuO_6+δ covering a wide range of hole concentration. Magnetization curves in the non-SC HOD regime have shown a tendency to be saturated in high magnetic fields at low temperatures, which is probably a precursor of the possible ferromagnetic transition at a lower temperature. In addition, it has been found that ρ_ab exhibits the temperature dependence being proportional to T^4.3, which is characteristic of a metal with two-dimensional ferromagnetic fluctuations, in a wide range of hole concentration from the superconducting overdoped to the non-SC HOD regime. It has been concluded that two-dimensional ferromagnetic correlation develops at low temperatures in HOD Bi-2201 and that therefore the development of the ferromagnetic correlation is probably an intrinsic feature in the HOD cuprates