Nanoscaling Laws of Magnetic Nanoparticles and Their Applicabilities in Biomedical Sciences
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- 作者：Young-wook Jun ; Jung-wook Seo ; Jinwoo Cheon
- 刊名：Accounts of Chemical Research
- 出版年：2008
- 出版时间：February 2008
- 年：2008
- 卷：41
- 期：2
- 页码：179 - 189
- 全文大小：4019K
- 年卷期：v.41,no.2(February 2008)
- ISSN：1520-4898
文摘
Magnetic nanoparticles, which exhibit a variety of unique magnetic phenomena that are drastically different from those of their bulk counterparts, are garnering significant interest since these properties can be advantageous for utilization in a variety of applications ranging from storage media for magnetic memory devices to probes and vectors in the biomedical sciences. In this Account, we discuss the nanoscaling laws of magnetic nanoparticles including metals, metal ferrites, and metal alloys, while focusing on their size, shape, and composition effects. Their fundamental magnetic properties such as blocking temperature (Tb), spin life time (τ), coercivity (Hc), and susceptibility (χ) are strongly influenced by the nanoscaling laws, and as a result, these scaling relationships can be leveraged to control magnetism from the ferromagnetic to the superparamagnetic regimes. At the same time, they can be used in order to tune magnetic values including Hc, χ, and remanence (Mr). For example, life time of magnetic spin is directly related to the magnetic anisotropy energy (KuV) and also the size and volume of nanoparticles. The blocking temperature (Tb) changes from room temperature to 10 K as the size of cobalt nanoparticles is reduced from 13 to 2 nm. Similarly, Hc is highly susceptible to the anisotropy of nanoparticles, while saturation magnetization is directly related to the canting effects of the disordered surface magnetic spins and follows a linear relationship upon plotting of ms1/3 vs r−1. Therefore, the nanoscaling laws of magnetic nanoparticles are important not only for understanding the behavior of existing materials but also for developing novel nanomaterials with superior properties.