Values For Some Common Materials
The following table should be used with caution as the permeability of ferromagnetic materials varies greatly with field strength. For example 4% Si steel has an initial relative permeability (at or near 0T) of 2,000 and a maximum of 35,000 and, indeed, the relative permeability of any material at a sufficiently high field strength tends to 1.
| Medium | Susceptibility χm (volumetric SI) |
Permeability μ | Relative Permeability μ/μ0 | Magnetic field | Frequency max. |
|---|---|---|---|---|---|
| Metglas | 1.25 | 1,000,000 | at 0.5 T | 100 kHz | |
| Nanoperm | 10×10−2 | 80,000 | at 0.5 T | 10 kHz | |
| Mu-metal | 2.5×10−2 | 20,000 | at 0.002 T | ||
| Mu-metal | 50,000 | ||||
| Permalloy | 1.0×10−2 | 8,000 | at 0.002 T | ||
| Electrical steel | 5.0×10−3 | 4,000 | at 0.002 T | ||
| Ferrite (nickel zinc) | 2.0×10−5 – 8.0×10−4 | 16–640 | 100 kHz ~ 1 MHz | ||
| Ferrite (manganese zinc) | >8.0×10−4 | 640 (or more) | 100 kHz ~ 1 MHz | ||
| Steel | 8.75×10−4 | 100 | at 0.002 T | ||
| Nickel | 1.25×10−4 | 100 – 600 | at 0.002 T | ||
| Neodymium magnet | 1.05 | ||||
| Platinum | 1.2569701×10−6 | 1.000265 | |||
| Aluminum | 2.22×10−5 | 1.2566650×10−6 | 1.000022 | ||
| Wood | 1.00000043 | ||||
| Air | 1.00000037 | ||||
| Concrete | 1 | ||||
| Vacuum | 0 | 1.2566371×10−6 (μ0) | 1 | ||
| Hydrogen | −2.2×10−9 | 1.2566371×10−6 | 1.0000000 | ||
| Teflon | 1.2567×10−6 | 1.0000 | |||
| Sapphire | −2.1×10−7 | 1.2566368×10−6 | 0.99999976 | ||
| Copper | −6.4×10−6 or −9.2×10−6 |
1.2566290×10−6 | 0.999994 | ||
| Water | −8.0×10−6 | 1.2566270×10−6 | 0.999992 | ||
| Bismuth | −1.66×10−4 | 0.999834 | |||
| Superconductors | −1 | 0 | 0 |
A good magnetic core material must have high permeability.
For passive magnetic levitation a relative permeability below 1 is needed (corresponding to a negative susceptibility).
Permeability varies with magnetic field. Values shown above are approximate and valid only at the magnetic fields shown. Moreover, they are given for a zero frequency; in practice, the permeability is generally a function of the frequency. When frequency is considered the permeability can be complex, corresponding to the in phase and out of phase response.
Note that the magnetic constant has an exact value in SI units (that is, there is no uncertainty in its value), because the definition of the ampere fixes its value to 4π × 10−7 H/m exactly.
Read more about this topic: Permeability (electromagnetism)
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