Magnetocaloric effect and Griffiths-like phase in La0.67Sr0.33MnO3 nanoparticles
Magnetocaloric effect and Griffiths-like phase in La0.67Sr0.33MnO3 nanoparticles
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DOI：
10.1063/1.3037236
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发表时间：
2008-12
影响因子：
3.2
通讯作者：
Wenjian Lu;X. Luo;C. Hao;W. Song;Y. Sun
中科院分区：
文献类型：
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作者：
Wenjian Lu;X. Luo;C. Hao;W. Song;Y. Sun
研究了平均晶粒尺寸为32-85 nm的La_（0.67）Sr_（0.33）MnO_3纳米颗粒的晶粒尺寸对电磁性能的影响。金属-绝缘体转变温度TP随着晶粒尺寸的减小而逐渐降低，而铁磁-顺磁转变温度TC几乎保持不变。对于32 nm的样品，观察到较大的有效磁矩和偏离居里-外斯定律的逆磁化率，表明可能存在格里菲斯类团簇相。通过测量磁热效应（MCE）进一步研究了样品的铁磁转变。短程磁有序的存在大大降低了顺磁相的磁熵。利用朗道相变理论对磁致伸缩效应进行了分析，证实了磁弹性耦合和电子相互作用在锰氧化物磁热性质中的重要性。
The effect of grain size on electrical and magnetic properties of La0.67Sr0.33MnO3 nanoparticles with average grain size 32–85 nm has been investigated. The metal-insulator transition temperature TP gradually decreases with decreasing grain size, while the ferromagnetic-paramagnetic transition temperature TC remains almost constant. For the 32 nm sample, the larger effective magnetic moments and the deviation of the inverse susceptibility from the Curie–Weiss law are observed, indicating the possible existence of a Griffiths-like cluster phase. The ferromagnetic transition of the samples is further investigated by measuring magnetocaloric effect (MCE). The presence of short-range magnetic order greatly depresses the magnetic entropy of the paramagnetic phase. Moreover, the analysis of the MCE using Landau theory of phase transition confirms the importance of magnetoelastic coupling and electron interaction in magnetocaloric properties of manganites.