Magnetic properties and microstructure of carbon encapsulated Ni nanoparticles and pure Ni nanoparticles coated with NiO layer
Magnetic properties and microstructure of carbon encapsulated Ni nanoparticles and pure Ni nanoparticles coated with NiO layer
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DOI：
10.1016/s0025-5408(02)00702-x
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发表时间：
2002-04-01
影响因子：
5.4
通讯作者：
Dong, XL
中科院分区：
文献类型：
--
作者：
Sun, XC;Dong, XL
成功制备了两种纳米镍颗粒——碳包覆镍纳米颗粒Ni(C)和包覆NiO层Ni(O)的纯镍纳米颗粒。结构表征（HR-TEM、SAED 和 XRD）揭示了它们独特的形态特性。两种 Ni 纳米颗粒组装体的磁化测量显示，Ni(O) 颗粒组装体在不可逆温度 T-irr,T- 之下，零场冷却和场冷却磁化强度之间存在偏差，显示出更大的矫顽力和剩磁。这种偏差可以解释为由于 Ni(O) 颗粒组件之间的铁磁偶极子-偶极子相互作用效应而产生的典型纳米团簇玻璃行为（集体行为）。然而，Ni(C) 颗粒在高于 T-B 平均阻挡温度（在 1000 Oe 下确定为 115 K 左右）时表现出改进的超顺磁性。此外，观察到饱和磁化强度逐渐降低，这归因于封装颗粒的纳米晶体性质，以及镍纳米晶体中可能存在的碳溶液。 (C) 2002 Elsevier Science Ltd. 保留所有权利。
Two kinds of nickel nanoparticles-carbon encapsulated Ni nanoparticles Ni(C) and pure Ni nanoparticles coated with NiO layers Ni(O) are successfully prepared. Structural characterizations (HR-TEM, SAED, and XRD) reveal their distinct morphological properties. Magnetization measurements for the assemblies of two kinds of Ni nanoparticles show a larger coercivity and remanence by a deviation between the zero-field-cooled and the field-cooled magnetization below the irreversibility temperature, T-irr,T- for the assemblies of Ni(O) particles. This deviation may be explained as a typical nanocluster-glass behavior (collective behavior) due to ferromagnetic dipole-dipole interaction effects among the assemblies of Ni(O) particles. However, Ni(C) particles exhibit modified superparamagnetic properties above the average blocking temperature of T-B, which is determined to be around 115 K at 1000 Oe. Moreover, a gradual decrease in saturation magnetization is observed, which is attributed to the nanocrystalline nature of the encapsulated particles, coupled with possible carbon solution in Ni nanocrystals. (C) 2002 Elsevier Science Ltd. All rights reserved.