Comparison of the magnetic and electrical transport properties of La 2/3Ca 1/3Mn 1− xCr xO 3 and La 2/3+ xCa 1/3− xMn 1− xCr xO 3 ( [formula omitted] and 0.06)

Abstract

Polycrystalline samples with formulas La 2/3Ca 1/3Mn 1− x Cr x O 3 and La 2/3+ x Ca 1/3− x Mn 1− x Cr x O 3 ( x = 0 and 0.06) have been prepared. The structural, magnetic, electrical transport and magnetoresistance properties have been investigated comparatively. Compared with La 2/3Ca 1/3Mn 1− x Cr x O 3, the magnetization and conductivity are enhanced in La 2/3+ x Ca 1/3− x Mn 1− x Cr x O 3 at low temperatures. It is found that there are two peaks in the resistivity versus temperature curve for La 2/3Ca 1/3Mn 1− x Cr x O 3 and the additional peak disappears for La 2/3+ x Ca 1/3− x Mn 1− x Cr x O 3 ( x = 0.06 ). The experiment results are discussed by considering a variety of tolerance factors, the ratio of [Mn 3+]/([Mn 4+]+[Cr 3+]), the effects of A-site radius and the A-site mismatch effect. We suggest that these peculiar effects of Cr doping could be the consequence of a possible double exchange interaction between Mn 3+ and Cr 3+.