Magnetic interactions studies of Co and Ni-doped manganites using soft XMCD

An investigation of the electronic structure and magnetic moments of Co2+ and Ni2+ cations in doped CMR manganites Pr0.5Ca0.5(Mn1−xBx)O3 (B=Co with x=0.05 and B=Ni with x=0.04) was realized using soft X-ray Absorption Spectroscopy (sXAS) and soft X-ray Magnetic Circular Dichroism (sXMCD) at Co, Ni and Mn L2,3-edges. Compared to similar XAS experiments in Cr doped manganites, a smaller charge transfer character from Co or Ni 3d band to the oxygen 2p band is evidenced at low doping rate which suggest that Co and Ni ions would not participate directly in the double exchange phenomena contrary to Cr3+ ions. showed that Co and Ni magnetic moments align parallel to the Mn magnetic moments, contrary to the Cr magnetic moment which was shown to align antiparallel to the Mn sublattice in Cr doped samples. A simple phenomelogical model, based on electronic phase segregations, is proposed to understand the nature of the magnetic interactions in the doped manganites. It shows that the physical properties induced by Co and Ni doping in manganites are not controlled by the same mechanism as in Cr doped manganites.