Ferromagnetism and insulating behavior with a logarithmic temperature dependence of resistivity in Pb10−xCux(PO4)6O

Recent claim of discovering above-room-temperature superconductivity ( T c ≈400 K) at ambient pressure in copper doped apatite Pb 10 (PO 4 ) 6 O 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 (PO 4 ) 6 O. Here we report the characterization results from the Pb 10− x Cu x (PO 4 ) 6 O with a fraction of about 97 wt.% inferred from the fitting to the X-ray diffraction pattern, if assuming Cu 2 S as the only impurity. 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. Our results show the absence of metallicity and superconductivity in Pb 10− x Cu x (PO 4 ) 6 O at ambient pressure, and suggest the presence of strong correlation effect.