Classical magnetism

A theory of magnetism was developed long before the advent of quantum mechanics. This section contains an outline of this theory and defines some of the experimental quantities which may well be encountered. 

When a substance is placed in a magnetic field, H, the total magnetic induction within the substance, B, is proportional to the sum of H and M, where M is the magnetization of the substance  

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Erasable optical disk (EOD) systems, on the other hand, are challenging classic magnetic media in some areas of appHcation, primarily magnetic tape and the hard disk, but mostly optical media complement magnetic media. 

The physical interpretation of the anisotropic principal values is based on the classical magnetic dipole interaction between the electron and nuclear spin angular momenta, and depends on the electron-nuclear distance, rn. Assuming that both spins can be described as point dipoles, the interaction energy is given by Equation (8), where 6 is the angle between the external magnetic field and the direction of rn. 

How can metastable ions be registered with a classic magnetic sector mass spectrometer (See Chapter 2, Section 2.2.2) Let ion mj+ leave the ion source and after acceleration with accelerating voltage V fragment, with formation of ion m2+ and a neutral particle m3° between the source and magnetic analyzer (first field-free region, 1 FFR). 

This result of the quantum mechanical treatment coincides with the derivation of magnetic susceptibility in terms of classical magnetic moments if their moduli are taken equal to those associated to the individual spins. 

The unit vector components of the classical magnetic fields Ba>, Ba and B<3> in vacuo are all axial vectors by definition, and it follows that their unit vector components must also be axial in nature. In matrix form, they are, in the Cartesian basis... 

Classical magnets were not well suited to fast scanning, which is necessary for GC coupling, for instance, because of the hysteresis phenomenon and the magnet heating up... 

Fig. 14.11. Nanomagnet as a classical magnet en miniature on the cover-page of ChemPhysChem. The (Mo)Mo5 i2 Fe 3o cluster (see also Figure 14.2) in two representations, including one showing the orien-...

Clusters as magnets Mo75V" 2o with 10 V" triangles linked Mo72Fe "3o is a model for a classical magnet V is shows a layered magnetic structure 3a, 3c, 14 ... 

Spi n CohGrGnCGS. in all NMR experiments the spin system evolves under internal and external spin interactions. For isolated spins, the spin dynamics can be described in terms of the motion of classical magnetization vectors. Many structural and molecular dynamics problems in NMR involve couples spins. In this case, it is necessary to recourse to a quantum—mechanical formalism where a density operator describes the state of the system (1). 

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