Ferromagnetism and insulating behavior with a logarithmic temperature dependence of resistivity in $Pb_{10-x}Cu_x\left( PO_4 \right) _6O$

TL;DR

This study investigates copper-doped lead phosphate apatite, finding it to be a ferromagnetic semiconductor with a logarithmic temperature dependence of resistivity, and finds no evidence of superconductivity at ambient pressure.

Contribution

It provides detailed characterization of $Pb_{10-x}Cu_x(PO_4)_6O$, demonstrating the absence of superconductivity and metallicity, and highlights the material's ferromagnetic and insulating behavior.

Findings

Resistivity follows a ln(1/T) dependence over a wide temperature range.

The material exhibits ferromagnetic signals with weak superparamagnetic background.

No evidence of superconductivity was observed in the samples.

Abstract

Recent claim of discovering above-room-temperature superconductivity (Tc about 400 K) at ambient pressure in copper doped apatite $Pb_{10}\left( PO_4 \right) _6O$ has stimulated world-wide enthusiasm and impulse of motion. A lot of follow-up works have been carried out with controversial conclusions. To check whether superconductivity is really present or absent in the material, we need samples which should have a rather pure phase of $Pb_{10-x}Cu_x\left( PO_4 \right) _6O$. Here we report the characterization results from the $Pb_{10-x}Cu_x\left( PO_4 \right) _6O$ with a fraction of about 97 wt.% inferred from the fitting to the x-ray diffraction pattern. The resistivity measurements show that it is a semiconductor characterized roughly by a ln(1/T) temperature dependence in wide temperature region without trace of superconductivity. Magnetization measurements show that it has a general ferromagnetic signal with a weak superparamagnetic background. Many grains of the sample show clear interactions with a NbFeB magnet. The detected Cu concentration is much lower than the expected nominal one and the conduction may be improved if more Cu atoms are successfully doped into the system. Our results show the absence of metallicity and superconductivity in $Pb_{10-x}Cu_x\left( PO_4 \right) _6O$ at ambient pressure, and suggest the presence of strong correlation effect.