Jeddi M, Gharsallah H, Bejar M, Bekri M, Dhahri E, Hlil E K
Laboratoire de Physique Appliquée, Faculté des Sciences, Université de Sfax B. P. 1171 3000 Sfax Tunisia
Institut Préparatoire aux Études d'Ingénieur de Sfax, Université de Sfax B. P. 1172 3018 Sfax Tunisia.
RSC Adv. 2018 Mar 6;8(17):9430-9439. doi: 10.1039/c8ra00001h. eCollection 2018 Feb 28.
A detailed study of structural, magnetic and magnetocaloric properties of the polycrystalline manganite LaCaSrMnO is presented. The Rietveld refinement of X-ray diffraction pattern reveals that our sample is indexed in the orthorhombic structure with space group. Magnetic measurements display a second order paramagnetic (PM)/ferromagnetic (FM) phase transition at Curie temperature = 304 K. The magnetic entropy change (Δ ) is calculated using two different methods: Maxwell relations and Landau theory. An acceptable agreement between both data is noted, indicating the importance of magnetoelastic coupling and electron interaction in magnetocaloric effect (MCE) properties of LaCaSrMnO. The maximum magnetic entropy change (-Δ ) and the relative cooling power (RCP) are found to be respectively 5.26 J kg K and 262.53 J kg for = 5 T, making of this material a promising candidate for magnetic refrigeration application. The magnetic entropy curves are found to follow the universal law, confirming the existence of a second order PM/FM phase transition at which is in excellent agreement with that already deduced from Banerjee criterion. The critical exponents are extracted from the field dependence of the magnetic entropy change. Their values are close to the 3D-Ising class. Scaling laws are obeyed, implying their reliability. The spontaneous magnetization values determined using the magnetic entropy change (Δ ) are in good agreement with those obtained from the classical extrapolation of Arrott curves ( / ). The magnetic entropy change can be effectively used in studying the critical behavior and the spontaneous magnetization in manganites system.
本文对多晶锰酸盐LaCaSrMnO的结构、磁性和磁热性能进行了详细研究。X射线衍射图谱的Rietveld精修表明，我们的样品属于具有特定空间群的正交结构。磁性测量显示在居里温度(T_C = 304)K时存在二级顺磁（PM）/铁磁（FM）相变。使用两种不同方法计算磁熵变（(\Delta S)）：麦克斯韦关系和朗道理论。注意到两种数据之间有可接受的一致性，表明磁弹耦合和电子相互作用在LaCaSrMnO的磁热效应（MCE）性能中的重要性。对于(\Delta H = 5)T，发现最大磁熵变（(-\Delta S_{max})）和相对制冷功率（RCP）分别为5.26 J kg(^{-1})K(^{-1})和262.53 J kg(^{-1})，这使得该材料成为磁制冷应用的有前途的候选材料。发现磁熵曲线遵循通用定律，证实了在(T_C)处存在二级PM/FM相变，这与从Banerjee判据推导的结果非常一致。从磁熵变的场依赖性中提取临界指数。它们的值接近三维伊辛类。遵循标度律，这意味着它们的可靠性。使用磁熵变（(\Delta S)）确定的自发磁化值与从Arrott曲线（(M^2/H)）的经典外推获得的值非常一致。磁熵变可有效地用于研究锰酸盐系统中的临界行为和自发磁化。
