Effects of the A-site cation number on the properties of Ln5/8M3/8MnO3 manganites

The properties of manganites can be tuned by changing the doping level x in Ln1−xMxMnO3. A second mechanism allows tuning of magnetic and electronic properties, for fixed x values, by varying the average A-cation radius, 〈rA〉. Moreover, for fixed x and 〈rA〉 values, the changes in the A-cation size variance, σ2, also modify the ferromagnetic and metal–insulator transition temperatures. Here, we investigate the influence of the number of A-site cations on Ln5/8M3/8MnO3 manganites, where x, 〈rA〉 and σ2 values are kept constant, and in the absence of phase separation phenomena. We have found that the number of cation species at the A site (NA) has a strong influence on the width of the ferromagnetic and metal–insulator transitions, and a small influence on the average transition temperature. This behavior is opposite to that observed for increasing values of the variance σ2 in manganites, with the same x and 〈rA〉 values, where average transition temperatures are strongly reduced.