Hollow magnetic nanocrystals

5 Size- and Shape-Dependent Magnetic Properties of Magnetic Metal Nanoparticles 

When an external magnetic field interacts with the single-domain particle, an additional potential energy of Ef = - H is supplied. Depending on the 

More explicitly, the Neel (Tn) and Brownian (Xb) magnetic relaxation times of a magnetic partide are described as  

If the concentration of nanopartides in a sample is high, the magnetic moments of individual nanopartides can interact, such that these dipolar interactions will greatly affect the magnetic behavior of the sample [155]. Interpartide interactions in both two-dimensional (2-D) and three-dimensional (3-D) assemblies of magnetic nanoparticles result in the Tg being shifted to higher values. Thus, an increase of the Tg by 

Fe4gPt52 nanoc stals. The individual line scans Courtesy of C. B. Murray. 

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Hollow Magnetic Nanocrystals Hollow nanoscale stmctures were first obtained by Y. Yin during the sulfurization of cobalt nanocrystals at elevated temperatures [145]. This process was found to lead to the formation of hollow cobalt sulfide nanocrystals such that, depending on the size of the cobalt nanocrystals and the cobalt sulfur molar ratio, different stoichiometries of hollow cobalt sulfide could be obtained. Hollow nanostmctures are usually formed through the nanoscale Kirkendall effect, which is based on the difference in diffusion rates of two species, and results in an accumulation and condensation of vacancies [146]. This phenomenon was first observed by Kirkendall at the interface of copper and zinc in brass in 1947 [147]. As a typical example of the nano-Kirkendall effect, the controllable oxidation of iron nanoparticles by air can lead to the formation of hollow iron oxide nanostructures, as shown in Figure 3.137. During the course of metal nanoparticle oxidation, the outward diffusion of metal occurs much faster in... 

Gao JH, Zhang B, Zhang XX et al (2006) Magnetic-dipolar-interaction-induced self-assembly affords wires of hollow nanocrystals of cobalt selenide. Angew Chem Int Ed. 45(8) 1220-1223... 

The morphologies of magnetic multicomponent nanocrystals can be subdivided into several groups, namely core hdl nanoparticles, dumbbell nanopartkles, and the more recently discovered hollow nanostructures. The general approach towards the... 

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