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首页> 外文期刊>RSC Advances >Copper-doped lanthanum manganite La0.65Ce0.05Sr0.3Mn1?xCuxO3 influence on structural, magnetic and magnetocaloric effects
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Copper-doped lanthanum manganite La0.65Ce0.05Sr0.3Mn1?xCuxO3 influence on structural, magnetic and magnetocaloric effects

机译：铜掺杂镧锰矿La0.65Ce0.05Sr0.3Mn1？xCuxO3对结构，磁和磁热效应的影响

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摘要

Bulk nanocrystalline samples of La _(0.65) Ce _(0.05) Sr _(0.3) Mn _(1? x ) Cu _( x ) O _(3) (0 ≤ x ≤ 0.15) manganites are prepared by the sol–gel based Pechini method. The effect of the substitution for Mn with Cu upon the structural and magnetic properties has been investigated by means of X-ray diffraction (XRD), Raman spectroscopy and dc magnetization measurements. The structural parameters obtained using Rietveld refinement of XRD data showed perovskite structures with rhombohedral ( R c ) symmetry without any detectable impurity phase. Raman spectra at room temperature reveal a gradual change in phonon modes with increasing copper concentration. The analysis of the crystallographic data suggested a strong correlation between structure and magnetism, for instance a relationship between a distortion of the MnO _(6) octahedron and the reduction in the Curie temperature, T _(c) . A paramagnetic to ferromagnetic phase transition at T _(C) is observed. The experimental results confirm that Mn-site substitution with Cu destroys the Mn ~(3+) –O ~(2?) –Mn ~(4+) bridges and weakens the double exchange (DE) interaction between Mn ~(3+) and Mn ~(4+) ions, which shows an obvious suppression of the FM interaction in the La _(0.65) Ce _(0.05) Sr _(0.3) Mn _(1? x ) Cu _( x ) O _(3) matrix. The maximum magnetic entropy change ?Δ S ~(max) _(M) is found to decrease with increasing Cu content from 4.43 J kg ~(?1) K ~(?1) for x = 0 to 3.03 J kg ~(?1) K ~(?1) for x = 0.15 upon a 5 T applied field change.
机译：通过溶胶法制备了La _（0.65）Ce _（0.05）Sr _（0.3）Mn _（1？x）Cu _（x）O _（3）（0≤x≤0.15）锰的纳米晶样品。基于凝胶的Pechini方法。通过X射线衍射（XRD），拉曼光谱和直流磁化测量研究了用Cu替代Mn对结构和磁性的影响。使用Rietveld精修XRD数据获得的结构参数显示钙钛矿结构具有菱形（R c）对称性，没有任何可检测到的杂质相。室温下的拉曼光谱显示，随着铜浓度的增加，声子模式逐渐变化。晶体学数据的分析表明，结构与磁性之间存在很强的相关性，例如MnO_（6）八面体的变形与居里温度T_（c）降低之间的关系。在T_（C）处观察到顺磁性到铁磁性的相变。实验结果证实，Cu取代Mn会破坏Mn〜（3+）–O〜（2？）–Mn〜（4+）桥，并削弱Mn〜（3+）之间的双交换（DE）相互作用。和Mn〜（4+）离子，对La _（0.65）Ce _（0.05）Sr _（0.3）Mn _（1？x）Cu _（x）O _（ 3）矩阵。发现最大的磁熵变ΔΔS〜（max）_（M）随着Cu含量的增加而减小，从x = 0的4.43 J kg〜（？1）K〜（？1）到3.03 J kg〜（？）。 1）在施加5 T的磁场变化后，对于x = 0.15，K〜（？1）。

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