Magnetic Permeability

Magnetic permeability is typically denoted by the Greek symbol μ (mu) and is given by 

B represents the magnetic field strength, and H represents the magnetic field intensity.

Units

The SI unit of magnetic permeability is henry per meter (H/m) or newton per ampere squared (N/A²).

The magnetic permeability of free space (μ₀) is a fundamental constant that determines how magnetic fields are formed in a vacuum. It is also known as the vacuum permeability constant. The value of μ₀ is approximately 4π × 10^-7 N/A². This constant plays a crucial role in electromagnetic theory and has various applications.

One of its most important applications is determining the speed at which electromagnetic waves propagate in free space. The speed of light in a vacuum, denoted by the symbol c, is related to μ₀ and the permittivity of free space (ε₀) through the equation 

This equation shows that the speed of light depends on the properties of free space, specifically its magnetic permeability and electric permittivity. Its value is approximately 3 × 10⁸ meters per second. Electromagnetic waves, such as light, radiowaves, and microwaves, travel at this speed when passing through a vacuum.

The relative permeability of a material is a dimensionless quantity. It is defined as the ratio of the material’s magnetic permeability to the permeability of free space. In other words, it measures how much a material can concentrate or amplify magnetic fields compared to a vacuum.

The relative permeability of air or vacuum is considered equal to 1.

Magnetic permeability values vary for different materials, and this property plays a crucial role in various applications involving magnets and electromagnetic systems. Here are a few relative permeability values for different materials:

Non-magnetic: Wood, plastic, glass, and most non-metallic substances have relative magnetic permeability values close to 1. They are generally considered to be non-magnetic.

Wood	1.00000043
Sapphire	0.99999976

Ferromagnetic: Ferromagnetic materials such as iron, nickel, and cobalt exhibit high relative magnetic permeability values, typically hundreds to thousands. This property makes them highly susceptible to becoming magnetized when exposed to a magnetic field.

Iron	5000
Nickel	100 – 600
Cobalt-Iron	18000

Paramagnetic: Paramagnetic materials like aluminum, platinum, and oxygen have relative magnetic permeability values slightly greater than 1 but significantly less than ferromagnetic materials. They are weakly attracted to magnetic fields.

Aluminum	1.000022
Platinum	1.000265
Titanium	1.00005

Diamagnetic: Diamagnetic materials such as copper, gold, and water have relative magnetic permeability values slightly less than 1. They are weakly repelled by magnetic fields.

Copper	0.999994
Bismuth	0.999834
Water	0.999992

It is important to note that the magnetic permeability values depend on factors such as temperature and the strength of the applied magnetic field.