Comparison of the magnetic and electrical transport properties of La2/3Ca1/3Mn1−xCrxO3 and La2/3+xCa1/3−xMn1−xCrxO3 ( and 0.06)

Polycrystalline samples with formulas La2/3Ca1/3Mn1−xCrxO3 and La2/3+xCa1/3−xMn1−xCrxO3 ( x = 0 and 0.06) have been prepared. The structural, magnetic, electrical transport and magnetoresistance properties have been investigated comparatively. Compared with La2/3Ca1/3Mn1−xCrxO3, the magnetization and conductivity are enhanced in La2/3+xCa1/3−xMn1−xCrxO3 at low temperatures. It is found that there are two peaks in the resistivity versus temperature curve for La2/3Ca1/3Mn1−xCrxO3 and the additional peak disappears for La2/3+xCa1/3−xMn1−xCrxO3 ( x = 0.06 ). The experiment results are discussed by considering a variety of tolerance factors, the ratio of [Mn3+]/([Mn4+]+[Cr3+]), 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 Mn3+ and Cr3+.