Magnetization and M?ssbauer study of double layer perovskites La1.5Ca1.5Mn2 ? x Fe x O7 prepared by sol–gel method

摘要

Magnetization and M?ssbauer studies have been made for understanding magnetic behavior of three double perovskite systems La1.5Ca1.5Mn2 ? x Fe x O7 corresponding to x = 0.05, 0.10 and 0.50. These have been prepared following sol–gel route. Substitution of Fe does not lead to any major change in the tetragonal cell but increased iron leads to greater distortion in octahedral site. The three samples undergo paramagnetic–ferromagnetic transition. Curie temperature (T c) for the system with 0.05 Fe is ～150 K which is lower than (190 K) for the system without iron; with 0.50 Fe T c goes below 50 K. Iron goes as Fe3 + and replaces Mn in ab plane. With increasing Fe the valence states of Mn get re-distributed in a way that number of the Jahn–Teller ions Mn3 + increases and that of the pairs of Mn3 + –O–Mn4 + experiencing double exchange decreases.