X-ray absorption magnetic circular dichroism of (La,Ce) MnO3 thin films

Creating a bipolarity of semiconductors has been a key technology to develop recent advanced semiconductor devices. Such bipolarity for manganese oxides, of which "hole-doped manganites" exhibit a rich variety of electric transport and magnetic properties, has been of great importance. Although theoretical calculation predicts the presence of ferromagnetic "electron-doped manganites" with doping tetravalent cations, the ferromagnetic origin in experiments has been controversial due to the lack of direct experimental evidence. Here, we investigate the ferromagnetism in (La,Ce) MnO3 thin films by measuring the magnetic circular dichroism in soft x-ray absorption (XMCD). Despite the presence of Mn2+, i.e., electron doping for manganese, the Mn2+ amount did not correlate with the Curie temperature, indicating the minor magnetic contribution of Mn2+. More crucially XMCD measurements clarified that the ferromagnetism is not caused by the presence of Mn2+ but by self-hole doping for manganese.