STUDY ON PROPERTIES OF THE PEROVSKITE La2/3Ca1/3Mn1-xCoxO3 SYSTEM

Abstract

In this paper, the electrical and magnetic properties of a perovskite series of La_2/3Ca_1/3Mn_1-xCo_xO₃ (with x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) have been studied, in order to investigate the influence of Co substitution for Mn. From XPD patterns, the crystalline structure of all samples has been investigated carefully. Our experiment results from VSM measurement showed that the ferromagnetic – paramagnetic phase transition temperature decreases with increasing the Co content. The temperature dependence of resistivity is well fitted by the functions of R(T)= R₀ e E_a /k_gT in the range of temperature from 150 K to 300 K, in which Ea is activation energy. Also, magnetoresistance in the low magnetic fields of 0 – 0.4T of all samples has been investigated. It is found that the Co content dependence of E_a and CMR_max (the maximum of magnetoresistance ratio) of these sample is similar. These results can be explained in terms of double-exchange interaction of Mn³⁺–O^2– –Mn⁴⁺ and super-exchange interactions of Co ³⁺/Co⁴⁺ −O^2– –Mn⁴⁺