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 Ln_0.5Sr_0.5Mn_0.9Cu_0.1O₃ (Ln = La, Pr, Nd, or Ho) perovskite manganites have been investigated to explore the influence of A-site cation radius (〈r_A〉) 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 (T_N) increases, whereas Curie (T_C) and irreversibility temperatures (T_irr) decrease with decreasing 〈r_A〉, i.e., with increasing σ². Furthermore, the value of the magnetization decreases and resistivity increases with decreasing 〈r_A〉. 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.