Particle size effects on La_0.7Ca_0.3MnO₃: size-induced changes of magnetic phase transition order and magnetocaloric study

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• 作者：Wei Tang ; Wenjian Lu ; Xuan Luo ; Bosen Wang ; Xuebin Zhu ; Wenhai Song ; Zhaorong Yang ; Yuping Sun
• 关键词：Particle size ; Magnetocaloric ; Nanoparticle
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2010
• 出版时间：August 2010
• 年：2010
• 卷：322
• 期：16
• 页码：2360-2368
• 全文大小：2770 K

文摘

The structure, magnetic properties, and magnetocaloric effect of La_0.7Ca_0.3MnO₃ ceramics with different particle sizes have been investigated. It is found that the Curie temperature increases first, and then decreases as particle size decreases and the type of magnetic phase transition changes from first-order to second-order, which may be attributed to surface pressure effects. The maximum magnetic entropy change and relative cooling power (RCP) show non-monotonic behaviors with decreasing the particle size. However, for the 3400 nm sample, the magnetic entropy change −ΔS_M reaches the maximum values of 6.41 and 8.63 J/kg K for the field changes of 2.0 and 4.5 T, respectively. Furthermore, the estimated large RCP values under lower magnetic fields in La_0.7Ca_0.3MnO₃ are comparable with those of typical magnetic refrigerant materials in the corresponding temperature range, suggesting those compounds might be promising candidates for magnetic refrigeration.