Divalent manganese in A-position of perovskite cell: X-ray absorption finite structure study of La_(0.6)Sr_(0.4-x)MnTi_xO_3 manganites

摘要

Local structure and magnetic properties of Ti doped A-site deficient La_(0.6)Sr_(0.4-x)MnTi_xO_(3-delta)manganites (0.15 >=x >=0) have been studied. The compositions belong to rhombohedral R3-bar c phase. Segregation of (La_(0.6)Sr_(0.4-x)Mn_y)(Mn_(1-y-z)Ti_x)O_(3+delta) phase and fallout of (z/3)Mn_3O_4 oxide was observed with x increase. Some amount (y) of Mn, being in divalent valence state, occupies the A (=La,Sr)-position of perovskite cell. Samples with x=0 and 0.05 are ferromagnetic with Curie temperature T_C=350 and 172 K, respectively. Samples with x=0.1 and 0.15 are in spin(cluster)-glass states at low temperatures.