Attah-Baah John M, Silva Romualdo S, Santos Cledson, Carvalho Maria H, Ferreira Nilson S
Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristóvão, SE, Brazil.
Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, E-28049 Madrid, Spain.
ACS Omega. 2025 Apr 30;10(18):18973-18985. doi: 10.1021/acsomega.5c00940. eCollection 2025 May 13.
A key challenge remains to improve or discover magnetic solids with optimal magnetocaloric effect (MCE) performance, providing a promising and environmentally friendly cooling technology. Herein, we report the crystal structure, magnetocaloric effect, and critical behavior of double perovskite NdSmNiMnO synthesized by the modified sol-gel process. X-ray diffraction structural investigation reveals that NdSmNiMnO crystallizes in the monoclinic / (14) space group. The magnetocaloric analysis unveils a maximum magnetic entropy change of -Δ = 2.38 J kg K (at 0-7 T) near the ferromagnetic to paramagnetic second-order phase transition at 180 K. Furthermore, the estimated relative cooling power value increases from ∼25 to ∼182 kg K when the applied field changes up to 0-7 T, suggesting a promisor magnetic refrigerant material. The critical behavior investigated by techniques such as the modified Arrott plot, the Kouvel-Fisher method, and the critical isotherm analysis reliably yields critical exponents β = 0.469, γ = 0.978, and δ = 3.09, in agreement with the scaling hypothesis. Lastly, the renormalization group theory analysis revealed a magnetic interaction distance decaying as () ∝ , which is between the three-dimensional (3D) Heisenberg and the mean-field models, suggesting that the critical behavior of NdSmNiMnO can be attributed to the competition between long- and short-range magnetic interactions.
一个关键挑战仍然是改进或发现具有最佳磁热效应（MCE）性能的磁性固体，以提供一种有前景且环保的冷却技术。在此，我们报告了通过改进的溶胶 - 凝胶法合成的双钙钛矿NdSmNiMnO的晶体结构、磁热效应和临界行为。X射线衍射结构研究表明，NdSmNiMnO在单斜 / (14) 空间群中结晶。磁热分析揭示，在180 K附近从铁磁到顺磁的二阶相变处，最大磁熵变 -Δ = 2.38 J kg K（在0 - 7 T时）。此外，当施加磁场变化到0 - 7 T时，估计的相对冷却功率值从约25增加到约182 kg K，表明这是一种有前景的磁性制冷材料。通过改进的阿罗特图、库维尔 - 费舍尔方法和临界等温线分析等技术研究的临界行为可靠地得出临界指数β = 0.469、γ = 0.978和δ = 3.09，与标度假设一致。最后，重整化群理论分析表明磁相互作用距离按 () ∝ 衰减，这介于三维（3D）海森堡模型和平均场模型之间，表明NdSmNiMnO的临界行为可归因于长程和短程磁相互作用之间的竞争。
