Microscopic mechanism of magnetization

It has already been mentioned that from the point of view of their magnetic properties, we can distinguish three main classes of substance diamagnetic, paramagnetic and magnetically ordered substances. We shall now consider the same question from a microscopic point of view, i.e., which processes cause magnetic properties and how these properties are related to their chemical stracture. We shall start with a diamagnetic. 

Dividing both sides by dt, we obtain the angular velocity of the electron orbit precession 

Using the gyromagnetic ratio the orbit angular velocity can be found  

This expression can be applied both to orbit and spin precession taking the g-factor into account. The angular velocity is named after J. Larmor and the magnetic precession is also referred to as Larmor precession. In particular, for orbit precession, the angular velocity is 

Strictly speaking, the radius (r ) is not the radius of an electron orbit besides, it depends on the inclination angle a. As an electron orbit can be inclined to the induction direction (to an external field), averaging over aU these parameters allows us to obtain 

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