Effect of strontium substitution on the structural and magnetic properties of La1.8Sr0.2MMnO6 (M = Ni, Co)-layered manganites

Sr-substituted perovskites, La1.8Sr0.2MMnO6 (M = Ni, Co), were synthesized using the solid-state reaction technique to present a systematic study on their morphological, structural and magnetic properties. The average grain size of the as-prepared La1.8Sr0.2NiMnO6 samples are in the range of 0.2-0.7 mu m and those for La1.8Sr0.2CoMnO6 manganites are 0.1-2.8 m, which is significantly less than that of unsubstituted La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) manganites. The XPS analysis enlightened about phase purity, binding energy and oxygen vacancy of La1.8Sr0.2MMnO6 manganites. The Sr-substituted LNMO has revealed a sharp ferromagnetic to paramagnetic phase transition at 160 +/- 2 K, which is about 120 K less than that of parent LNMO. The Sr-substituted LCMO exhibited such a transition at 220 +/- 2 K, which is 8 K less than that of parent LCMO. The temperature-dependent magnetization measurements suggest that the effect of Sr on the transition temperature in LNMO is more significant than that of LCMO.