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

TL;DR

This study explores how Fe impurities influence ferromagnetic fluctuations and induce spin-glass states in heavily overdoped Bi-2201 cuprates, revealing enhanced ferromagnetic behavior and proposing a ferromagnetic spin-cluster model.

Contribution

It provides new insights into impurity effects on magnetic fluctuations and introduces a ferromagnetic spin-cluster model for heavily overdoped cuprates.

Findings

Fe substitution induces spin-glass states at low temperatures.

Ferromagnetic fluctuations are enhanced by Fe substitution.

A ferromagnetic spin-cluster model is proposed for heavily overdoped Bi-2201.

Abstract

We investigated Fe-substitution effects on ferromagnetic fluctuations in the superconducting overdoped and non-superconducting heavily overdoped regimes of the Bi-2201 cuprates by the magnetization and electrical-resistivity measurements. It was found that the spin-glass state was induced at low temperatures by the Fe substitution. The Curie constant and the effective Bohr magneton, estimated from the magnetic susceptibility, as well as the dimensionality of the ferromagnetic fluctuations from the resistivity, suggest the enhancement of the ferromagnetic fluctuations owing to the Fe substitution. A ferromagnetic spin-cluster model is proposed in the heavily overdoped regime of Bi-2201, while an antiferromagnetic spin-cluster model has been proposed in the overdoped regime of Bi-2201 [Hiraka et al., Phys. Rev. B 81, 144501 (2010)].