The effect of average A-site cation radius on TC in perovskite manganites

Abstract

Three series of samples Ln 0.7T 0.3MnO 3 (I), Ln 0.7T 0.3Mn 0.9Cr 0.1O 3 (II), and Ln 0.7T 0.3Mn 0.9Fe 0.1O 3 (III) (Ln=La, (La, Nd), (La, Y), T=Ca, CaSr, Sr) were prepared by sol–gel technique. The effect of the average A-site cation radius 〈 r A〉 on the ferromagnetic transition temperature T C has been investigated. T C was obtained from M– T curves measured by vibrating sample magnetometer. For a little Nd 3+ doped at the A-site, the T C of Ln 0.7T 0.3MnO 3 (I) drops linearly with decreasing 〈 r A〉 (1.18 Å<〈 r A〉<1.25 Å). Similar behavior has been observed in series II and III, which have lower T C values than series I due to the weakening of the influence of double-exchange interactions upon substituting Fe and Cr for Mn.