Investigating the magnetic properties and magnetic cooling potential of La and Sm co-doped CaMnO3 manganites

Abstract La and Sm co-doped CaMnO 3 manganites with the general formula of La x Ca 0.93− x Sm 0.07 MnO 3 ( x = 0.0, 0.2, 0.4, 0.6, and 0.8) were synthesized by the conventional solid-state reaction method. X-ray diffraction confirmed orthorhombic perovskite structures, while SEM analysis revealed improved grain boundaries and reduced porosity with increasing La substitution. As the La concentration increases, well-defined polygonal grains become more prominent, accompanied by noticeable grain growth. Magnetization measurements demonstrated a systematic shift of the Curie temperature from 50 K ( x = 0.0) to above 168 K ( x = 0.6), originating from the optimization of the Mn 3+ /Mn 4+ ratio and the strengthening of double-exchange interactions. The La06 composition exhibited the best magnetocaloric response with − Δ S ₘ ≈ 0.85 J·kg⁻ 1 ·K⁻ 1 at 0.9 T and a critical exponent n ≈ 0.78, consistent with a second-order transition. These results highlight the critical role of A-site co-doping in enabling simultaneous microstructural and magnetic optimization in CaMnO 3 -based manganite. La and Sm co-doped CaMnO 3 exhibit tunable Curie temperature, low magnetic hysteresis, broad operating temperature range, and effective low-field magnetocaloric response, together with structural stability and cost efficiency, highlighting their potential as environmentally acceptable oxide-based candidates for cryogenic magnetic refrigeration. Furthermore, this study presents experimental results indicating that cost-effective perovskite systems can achieve magnetocaloric performance without relying on critical or toxic rare-earth elements such as Gd or Tb. This situation contributes to sustainability and the development of next-generation magnetic cooling technologies.