Size and shape effects on the order-disorder phase transition in CoPt nanoparticles
Size and shape effects on the order-disorder phase transition in CoPt nanoparticles
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DOI：
10.1038/nmat2574
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发表时间：
2009-12-01
期刊：
影响因子：
41.2
通讯作者：
Loiseau, A.
中科院分区：
文献类型：
--
作者：
Alloyeau, D.;Ricolleau, C.;Loiseau, A.
化学有序的纳米颗粒是磁存储应用的有希望的候选者。然而，使用亚10纳米的纳米磁体需要进一步研究其物理性质可能的尺寸效应。在这里，CoPt纳米粒子（T（C）（NP））的有序-无序相变温度的大小和形态的影响进行了实验研究，使用透射电子显微镜，并在理论上，与典型的Monte Carlo模拟。对于2.4-3-nm颗粒，发现T（C）（NP）比块体材料转变温度低325-175摄氏度，与我们的Monte Carlo模拟一致。此外，我们确定T（C）（NP）也对纳米颗粒的形状敏感，因为只有一个尺寸（即，面内尺寸或厚度）小于3 nm的颗粒足以引起T（C）（NP）的显著降低。这项工作强调了考虑到纳米物体的三维形态来理解和控制其结构特性的必要性。
Chemically ordered bimetallic nanoparticles are promising candidates for magnetic-storage applications. However, the use of sub-10nm nanomagnets requires further study of possible size effects on their physical properties. Here, the effects of size and morphology on the order-disorder phase transition temperature of CoPt nanoparticles (T(C)(NP)) have been investigated experimentally, using transmission electron microscopy, and theoretically, with canonical Monte Carlo simulations. For 2.4-3-nm particles, T(C)(NP) is found to be 325-175 degrees C lower than the bulk material transition temperature, consistent with our Monte Carlo simulations. Furthermore, we establish that T(C)(NP) is also sensitive to the shape of the nanoparticles, because only one dimension of the particle (that is, in-plane size or thickness) smaller than 3nm is sufficient to induce a considerable depression of T(C)(NP). This work emphasizes the necessity of taking into account the three-dimensional morphology of nano-objects to understand and control their structural properties.