Charge states of transition metal in “Cr, Co and Ni” doped Ln0.5Ca0.5MnO3 CMR manganites

The XAS study at Cr, Co, Ni and Mn K-edges was performed for the doped CMR manganites Ln_0.5Ca_0.5Mn_1-xB_xO₃ with Ln=La, Nd, Sm and B= Cr, Co, Ni (), on the samples that were studied previously for their ferromagnetic-metallic to antiferromagnetic-insulator transition. We observed that the formal charges of the doping elements are Ni²⁺, Co²⁺ and Cr³⁺. It is also evidenced that the average formal charge of the manganese is increased after doping, in agreement with the charge compensation keeping “O₃” stoichiometry. These results suggest that the doping elements participate directly to the band structure. Received: 9 January 1998 / Received in final form: 6 April 1998 / Accepted: 7 April 1998