Magnetism superparamagnetic contribution

Figure 6.13 shows the Mossbauer spectra of ferritin [51], which is an iron-storage protein consisting of an iron-rich core with a diameter around 8 nm with a structure similar to that of ferrihydrite and which is surrounded by a shell of organic material. At 4.2 K essentially all particles contribute to a magnetically split component, but at higher temperatures the spectra show the typical superposition of a doublet and a sextet with a temperature dependent area ratio. At 70 K the sextet has disappeared since all particles have fast superparamagnetic relaxation at this temperature. 

Superparamagnetism is a specific type of magnetic behaviour observed with fine magnetically ordered particles dispersed in a diamagnetic matrix [1], Understanding of this phenomenon has been a very important contribution to fundamental theories of magnetism and laid the foundation... 

The low-temperature magnetization curves of the composite powders show that the M T, H) dependence has two contributions the ferromagnetic (Co-rich or Cu-poor) and the superparamagnetic (ultra thin ferromagnetic not coupled clusters). The experimental M T, H) curves are well fitted by ... 

Profound attention has been given to the magnetic latexes because of their special properties like superparamagnetism, high field irreversibility, high saturation field and extra anisotropy contribution. These properties are, for example, controlled by size and surface type. 

The intrinsic part, XmH, is linear in the applied magnetic H and is just the contribution of pure LiFeP04. The extrinsic component that is easily saturated in /7 is the contribution of the ferrimagnetic nanoclusters, which can be estimated in a simple superparamagnetic model [10]. It can be written under the form ... 

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