Exploring the impact of synthesis method and dopant concentration on the magnetism and magnetocaloric effect of Sr-doped lanthanum manganites

Abstract

This study investigates the magnetic properties of strontium-doped lanthanum manganites [La1−xSrxMnO3 (LSMO)], focusing on the effects of doping and synthesis methods. Materials with different Sr-doping concentrations (x = 0, 0.1, 0.2, and 0.3) were prepared by citrate–nitrate autocombustion (CNA) and coprecipitation synthesis. Magnetization curves exhibit a transition from paramagnetic behavior to long-range ferromagnetic order below Curie temperatures (TC), which increase with Sr content due to Jahn–Teller distortions and electron delocalization. The synthesis method significantly influences magnetic properties, with CNA-prepared samples exhibiting a systematic decrease in coercivity and remanence with Sr doping, leading to very soft ferromagnetic behavior at x = 0.3. In contrast, coprecipitation-synthesized materials show deviations due to variable oxygen content, which affects Mn valence states and magnetic interactions. Hysteresis loops and magnetocaloric effects were also investigated, revealing that coprecipitation-derived samples exhibit a higher magnetocaloric effect due to structural defects and oxygen nonstoichiometry. A comparison with gadolinium and previous studies highlights the potential of LSMO materials for magnetic refrigeration applications despite their somewhat lower magnetic entropy changes.