Introduction

As a child I experienced with wonder the behaviour of bar magnets, and as I write this at the age of 61, my wonder has not diminished.

Sadly, this download-only Chapter is not a paean to the wonder of magnets, but a review from a technical perspective of the way ‘ordinary’ solids respond when exposed to a magnetic field.

The challenges

The first challenge in any quantitative discussion of magnetism is the units used to express magnetic quantities. I don’t quite understand why the situation is so bad, but the chapter begins with an exposition on units and I urge you as best you can, to stay as close to the SI as possible. 

The second challenge is that unlike ferromagnets with which almost everyone is familiar, most substances have very weak magnetic response. The usefulness of magnetic measurements in research is that they are sensitive to all aspects of the behaviour of electrons in solids: core electrons, electrons in unfilled shells, and magnetic moment of the electron too. But the corresponding downside of magnetic measurements is that one needs to account for all these responses in order to even understand the sign of the response to the applied field!

Ferromagnetism

In an alternate universe I I might easily have written about an entire book on ferromagnetism, but in this context I had to restrict myself to pointing that it does not arise from magnetic interactions between electrons. 

• • Web Chapter 2 Magnetism