Electron paramagnetic resonance assessment of the electronic charge of Cu in YBa2Cu3O7−δ

Abstract
Electron paramagnetic resonance (EPR) has been measured on powdered YBa2Cu3O7−δ at 9 GHz and at variable temperature 4.2 K ≤ T ≤ 293 K. The decrease of the mean Landé factor value ḡ from 2.22 to 2.07, between T = 4 K and T = Tc, is ascribed to a hole being transferred from copper to oxygen.