Effect of cooling rate on size-dependent atomic ordering of CoPt nanoparticles
Effect of cooling rate on size-dependent atomic ordering of CoPt nanoparticles
复制标题
冷却速率对 CoPt 纳米颗粒尺寸依赖性原子排序的影响
DOI：
10.1080/09500839.2012.685188
复制
发表时间：
2012
影响因子：
1.2
通讯作者：
T. J. Konno
中科院分区：
文献类型：
--
作者：
K. Sato;K. Yanajima;T. J. Konno
我们报告的冷却速率的影响上的尺寸依赖的原子有序的CoPt纳米粒子使用像差校正的高分辨率透射电子显微镜。结果表明，在退火后的冷却过程中，冷却速率对原子有序化起着至关重要的作用。在873 K下退火1 h后快速冷却（110 K/min），直径约为1.3 nm的纳米粒子呈现A1无序相，而在慢速冷却（1.5 K/min）时，则呈现L10有序相。在973 K退火1 h后，通过快速冷却也得到了无序相。这些结果明确地表明，对于直径小于3 nm的CoPt纳米颗粒，有序-无序转变温度降低到至少低于873 K的温度。缓慢的冷却过程促进了原子的有序化，这导致了高达2200 Oe的磁性增强。这项研究表明，通过控制热处理后的冷却速率，可以提高CoPt纳米颗粒的硬磁性能。
We report on the effect of cooling rate on the size-dependent atomic ordering of CoPt nanoparticles using aberration corrected high-resolution transmission electron microscopy. It was found that cooling rate plays a crucial role in promoting atomic ordering during the cooling process after annealing. Nanoparticles of ≈3 nm in diameter show the A1-disordered phase after annealing at 873 K for 1 h followed by rapid cooling (110 K/min), while the L10-ordered phase is obtained when the cooling rate is slow (1.5 K/min). The disordered phase is also obtained by rapid cooling after annealing at 973 K for 1 h. These results unambiguously indicate that the order–disorder transformation temperature is reduced to a temperature at least lower than 873 K for CoPt nanoparticles smaller than 3 nm in diameter. The slow cooling process promotes the atomic ordering, which resulted in an enhancement of magnetic coercivity as high as 2200 Oe. This study demonstrates that hard magnetic properties of the CoPt nanoparticles can be improved by controlling the cooling rate after heat treatments.