The metal–insulator transition in the strongly correlated layered compoundNaγCoO2 induced by dilute Mn doping

Abstract

Structure, transport and magnetic properties have been investigated for the layered materialsNaγCo1−xMnxO2 (). With increase of the Mn concentration, the in-plane lattice parametera decreases while thelattice parameter c increases. 3% Mn doping can result in a metal–insulator transition. The temperaturedependence of the magnetization of the samples obeys the Curie–Weiss law and theeffective moment of the magnetic ions increases with doping. Electron energy-lossspectroscopy measurement shows that the Co valence is about 3.3 and remains unchangedupon doping. However, the valence of Mn increases rapidly with doping and reaches3.7 ± 0.1 for thesample with x = 0.5. The results are discussed in terms of the disorder effect induced by doping of magneticions. This work demonstrates that the structure, transport and magnetic properties ofNaγCoO2 are very sensitive to doping with magnetic ions.