Mossbauer and magnetization studies of magnetic phase transitions in 0.5BiFeO₃-0.5NaNbO₃ and 0.5LaFeO₃-0.5NaNbO₃ solid solutions

0.5AFeO(3)-0.5NaNbO(3) (A = Bi, La) solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides. Mossbauer studies have shown that while for 0.5BiFeO(3)-0.5NaNbO(3) the magnetic phase transition temperature T-M value is about 150 K, for 0.5LaFeO(3)-0.5NaNbO(3), it is only approximate to 25 K. This dramatic difference in T-M values seems to be due to additional contribution of the magnetic superexchange between Fe3+ ions via the empty 6p-states of Bi3+ ions to the overall superexchange.