Effect of A-site cation size on magnetic and charge-ordering properties of Ln0.5Sr0.5Mn0.9Cu0.1O3 (Ln = La, Pr, Nd, or Ho)

The structural, magnetic, and electrical properties of Ln0.5Sr0.5Mn0.9Cu0.1O3 (Ln = La, Pr, Nd, or Ho) perovskite manganites have been investigated to explore the influence of A-site cation radius (〈rA〉) and the A-site cation size-disorder (σ2) on the various interdependent phenomena such as ferromagnetism (FM), phase separation (PS), and charge ordering (CO). The temperature dependence magnetization (M–T) curve of La-based sample shows four distinct points at ∼269 K, 255 K, 200 K, and 148 K corresponding to strong FM, cluster glass (CG), weak FM, and charged ordered antiferromagnetic (COAFM) transitions, respectively. Our investigation shows that Neel temperatures (TN) increases, whereas Curie (TC) and irreversibility temperatures (Tirr) decrease with decreasing 〈rA〉, i.e., with increasing σ2. Furthermore, the value of the magnetization decreases and resistivity increases with decreasing 〈rA〉. All samples exhibit insulating behavior in the temperature range 77–300 K and above 110 K the electronic conduction mechanism has been described within the framework of the variable range hopping (VRH) model.