Asymmetry of electron and hole doping in YMnO3

We synthesized hexagonal YMnO3 doped with tetravalent Zr ions and studied the electronic and magnetic properties. Zr substitution creates a mixed Mn3+-Mn2+ system, instead of the conventional Mn3+-Mn4+ of colossal magnetoresistance manganites. The YMnO3 system displays a pronounced asymmetry for electron and hole doping. Hole doping results in a conducting state, whereas electron doping retains the insulating state. This asymmetry is a consequence of the crystal field splitting of the Mn ions in trigonal bipyramidal coordination