Units
Two sets of units may be used to represent the magnetic permeability: Teslas times meters per Ampere (T \(\! \cdot \!\) m/A), and Henrys per meter (H/m):
The magnetic field intensity \({\bf H}\) is frequently given in Amperes per meter (A/m), whereas the magnetic flux density is given in Teslas (T). Therefore, the first choice in units is defined by the magnetic constitutive relationship. Henrys are used to represent a unit of magnetic inductance. Therefore, the magnetic permeability also characterizes the magnetic inductance per unit length of a material.
More commonly, the magnetic properties of rocks are represented using the magnetic susceptibility \(\chi\). Magnetic susceptibility represents the proportion of total magnetic flux density attributed to induced magnetization. A physical description of the magnetic susceptibility is discussed in Magnetism in Rocks. Magnetic susceptibility is related to the magnetic permeability by the following equation:
where \(\mu_0 = 4\pi \times 10^{-7}\) H/m is the permeability of free-space. The correct SI units for magnetic susceptibility are (A/m)/(A/m). However, it is commonly expressed as a unitless quantity. Magnetic susceptibilities are occasionally given in CGS units. The conversion between SI and CGS units is given by: