Engineering Physics

7.5 Classical theory of diamagnetism [Langevin theory]

In this theory, we will obtain an expression for the change in magnetic moment of an orbiting electron in a diamagnetic atom and the induced magnetic moment per unit volume of diamagnetic material in the applied magnetic field B₀.

A revolving electron in an orbit constitutes electric current in the orbit. This electric current produces magnetic field perpendicular to the plane of the orbit. The electrons in an atom are revolving in different orbits, oriented in random directions. So, the sum of the magnetic moments produced by all these orbiting electrons in an atom is zero. Let the angular velocity of an electron in an orbit of radius ‘r’ is ‘ω₀’ before applying magnetic field. The current ...