Dielectric properties of media
Radiofrequency dosimetry (SAR)

Materials are generally classified as either magnetic or non-magnetic. Unlike non-magnetic materials, magnetic materials have magnetic dipoles that are strongly affected by applied fields.

The materials encountered in radiofrequency dosimetry, human tissue but also textiles such as cotton, silk, leather, etc., are non-magnetic materials and their magnetic permeability is that of a vacuum (µ = µ₀ = 4.10^-7 H/m). This makes permittivity the key parameter for determining the distribution of the electromagnetic field in the body and therefore the power dissipated there.

Anisotropy is negligible in textiles and human tissue (for frequencies above MHz), which simplifies the general form of the electrical permittivity tensor into a complex scalar quantity: