Nanomagnetism

Koehler, F.M., Rossier, M., Waelle, M., Athanassiou, E.K., Limbach, L.K., Grass, R.N., Gunther, D. and Stark, W.J. (2009) Magnetic EDTA coupling heavy metal chelators to metal nanomagnets for rapid removal of cadmium, lead and copper from contaminated water. Chemical Communications, (32), 4862—4864. 

Baldovi, J. J., Clemente-Juan, J. M., Coronado, E., Gaita-Arino, A. and Gimenez-Saiz, C., (2014) Construction of a General Library for the Rational Design of Nanomagnets and Spin Qubits... 

Gatteschi, D., Sessoli, R. and Villain, J. (2006) Molecular Nanomagnets, Oxford University Press, New York, p. 72. 

Guidi, T. (2012) in Neutron Spectroscopy of Molecular Nanomagnets in Molecular Cluster Magnets (ed R.E.P. Winpenny), World Scientific. 

The purpose of this section is to review the parameters influencing the proton relaxation of a nanomagnet suspension. It will include an analysis of NMRD profiles, which provide the relaxivity dependence with the external held, expressed in proton Larmor frequency units. 

The aggregation of the nanomagnets has two different consequences on the proton relaxation properties on one hand, those related to the global structure of the cluster and to the magnetic field distribution around them and, on the other hand, those limited to the inner part of the aggregate (75). While the global effect dominantly affects i 2> the inner one influences R. ... 

The longitudinal relaxation rate inversely decreases with the residence time of water molecules inside the agglomerate. This effect was demonstrated thanks to a controlled and chemically induced process of agglomeration amongst ferrite nanomagnets coated by polyelectrolyte polymers. The NMRD profile becomes flatter on increasing agglomeration (Pig. 10). 

For USPIO particles containing only one nanomagnet per particle, the main parameters determining the relaxivity are the crystal radius, the specific magnetization and the anisotropy energy. Indeed, the high field dispersion is determined by the translational correlation time t. ... 

Soft X-ray Imaging. The nature of their interaction with matter makes soft X-rays ideal for imaging the interior structure of inorganic nanoscopic systems and biological cells. Consequently, soft X-ray microscopy has been most widely applied to chemical imaging in the fields of cell biology, environmental science, soft matter and polymers, and nanomagnetism. 

The study that we describe below was inspired by our work on fitting the dynamic susceptibilities measurements for real assemblies of fine particles. Those data typically describe polydisperse systems in the low-frequency bandwidth a>/2% = 1 — 103 Hz. As To 10 s or smaller, then, using formula (4.132) for estimations, one concludes that the frequency interval mentioned becomes a dispersion range for the interwell (superparamagnetic) mode at coto< ct > 1, that is, a > 10. For temperatures up to 300 K, this condition holds for quite a number of nanomagnetic systems. 

R. Skomski, Nanomagnetics , J. Phys. Condens. Matter 15, R841 (2003). 

The description of nanomagnets requires new approaches. First, nanostructures are not periodic and tend to have large surface-to-volume ratios. Because of this the magnetization is not uniform across the nanostructure, local magnetic moments differ from site to site, exchange coupling varies throughout the nanostructure, and the anisotropy can be quite different from bulk or surface anisotropies. Second, it is hard to define properties in the similar fashion as in the bulk or as in case of molecules. 

There is also some shape anisotropy due to magnetostatic dipole interactions (Ch. 3). This anisotropy is important in some nanomagnets, for example in elongated nanoparticles, but unrelated to the electronic structure. 

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