Development of Ferromagnetic Fluctuations in Heavily Overdoped (Bi,Pb)_2_Sr_2_CuO_6+delta_ Copper Oxides

TL;DR

This study reveals the presence of two-dimensional ferromagnetic fluctuations in heavily overdoped Bi-2201 cuprates, linking these fluctuations to the suppression of superconductivity in this regime.

Contribution

It provides experimental evidence of ferromagnetic fluctuations in heavily overdoped high-temperature cuprates, a phenomenon not previously established.

Findings

Ferromagnetic fluctuations detected via magnetization and muon spin relaxation.

Resistivity follows a 4/3 power law indicative of 2D FM fluctuations.

Enhanced spin fluctuations correlate with increased hole doping and reduced Tc.

Abstract

We demonstrate the presence of ferromagnetic (FM) fluctuations in the superconducting and non-superconducting heavily overdoped regimes of high-temperature superconducting copper oxides, using (Bi,Pb)_2_Sr_2_CuO_6+delta_ (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. Correspondingly, the ab-plane resistivity follows a 4/3 power law in a wide temperature range, which is characteristic of metals with two-dimensional FM fluctuations due to itinerant electrons. As the Wilson ratio evidences the enhancement of spin fluctuations with hole doping in the heavily overdoped regime, it is concluded that two-dimensional FM fluctuations reside in the heavily overdoped Bi-2201 cuprates, which is probably related to the decrease in the superconducting transition temperature in the heavily overdoped cuprates.