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(0.5)Sr(0.5)Mn(0.9)Cu(0.1)O(3) (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 (sigma(2)) 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 similar to 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 sigma(2). 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 110K the electronic conduction mechanism has been described within the framework of the variable range hopping (VRH) model. (c) 2012 Elsevier B.V. All rights reserved.