Influence of Ca Substitution on Order-Disorde...

Influence of Ca Substitution on Order-Disorder Temperature in Ln0.7Sr0.3-xCaxMnO3 Nanomanganite

Author Name : U. L. Shinde, N. B. Srivastava

Transport behavior in sol-gel prepared Ln0.7Sr0.3-xCaxMnO3 (Ln = Nd, La and 0≤ x ≤ 0.3) nanomanganite system have been investigated in the temperature range 10 – 330 K. It is found that with increase in Ca2+ ion concentration metal-insulator transition temperature (TMI) decreases. It is shown that the correlated polaron model accounts for the temperature dependence of resistivity and magnetoresistance in the entire temperature range. The atomic order transition temperature (Tca) increases with increase in cation mismatch parameter. Contrary to this the small polaron stabilization energy (εP) decreases sharply on cation mismatch. The atomic order-disorder crossover temperature, Tca, varies inversely with the square root of the polaron shift energy, εp, Tca√ εp = constant .