Electromagnetic Fields and Waves

# Magnetic field in the matter

Let’s consider magnets. Magnets are substances that create the magnetic field around them, without currents through the magnets. However, there are micro-currents that operate in the magnet. The magnetic field B0created by the system of currents in the vacuum, is different from the magnetic field, B, created by the same system of currents, but in the substance.

The micro-currents in the substance create additional magnetic field components B’, that are added to the magnetic field in a vacuum that then creates the magnetic field in the substance:

$\mathbit{B}\mathbf{=}{\mathbit{B}}_{\mathbf{0}}\mathbf{+}{\mathbit{B}}^{\mathbf{‘}}\mathbf{.}$

Let’s consider the uniform and isotropic environment. The elementary magnetic dipole is a small current turn. Magnetic properties of the substance are determined by properties and characteristics. These are small fragments of substance. It is important to know the intrinsic field of the magnetic dipole and the way it behaves in the external magnetic field. Intrinsic magnetic fields of this current turn, according to the Biot-Savart-Laplace Law, is:

$\mathbit{B}=\frac{{\mu }_{0}}{4\pi }\frac{2{p}_{m}}{{r}^{3}}$

The direction of magnetic field of the current coil is determined by the direction of the magnetic dipole, this current turn (or coil) is turned by the magnetic momentum, in accordance to the field

$\left(\mathbit{B}\mathbf{\parallel }{\mathbit{p}}_{m}\right).$

In a non-uniform field, there is a force affecting the coil that’s drawing the magnet in the field with a bigger intensity. If the magnet moment of the dipole is parallel, but in the opposite direction, it will be drawing out from the field. (Figure 35).