Exploring the role of Cu1+ in quasi-1D Cu1−xLixO (x = 0.025)

The influences of hole-doping in cupric oxide leads to a localization of charge carriers, accompanied by changes in crystal structure, magnetic and transport properties. The crystallographic structure and phase purity of the properly sintered sample is characterized by temperature-dependent neutron diffraction (ND) measurements where the composition is found as Cu_0.975Li_0.025O (CLO). Interestingly, the formation of Cu${}^{1+}$ and Cu${}^{3+}$ in addition to the Cu${}^{2+}$ was confirmed from the x-ray photoelectron spectroscopy (XPS) study in CLO system. Magnetization measurements show shifting in commensurate and incommensurate transition temperatures $T_{N1}$ $\sim$ 82 K and $T_{N2}$ $\sim$ 204 K respectively, highlighting the sensitive correlation between structural parameters and antiferromagnetically ordered quasi-1D spin arrangement. Temperature-dependent ordered magnetic moment (ground state) of Cu in CLO is calculated from ND data using a mean-field equation which coincides concomitantly with incommensurate antiferromagnetic transition $T_{N2}$. Above and below the said antiferromagnetic ordering temperature, a changeover was concluded from p-type to n-type conduction mechanism. The Cu${}^{1+}$ specimens in CLO maintain a high dielectric value ($\sim$ $10^3$) even at low temperature. The Cu${}^{3+}$ and charge order domains significantly influence the intriguing transport behavior (hole hopping between Cu${}^{3+}$ and Cu${}^{2+}$) of CLO, with their effects strongly dependent on the antiferromagnetically ordered spin structures.