Magnetic susceptibility is the degree of magnetization of a material in response to an applied magnetic field. If magnetic susceptibility is positive then the material can be paramagnetic, ferromagnetic, ferromagnetic, or antiferromagnetic.
Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetization of a material in response to an applied magnetic field.
It is defined as

`chi= M/H`

Here M is the magnetization of the material and H is the magnetic field strength.

where `chi`, a dimensionless quantity, is appropriately called the magnetic susceptibility. It is a measure of how a magnetic material responds to an external field.

It is small and positive for materials, which are called paramagnetic. It is small and negative for materials, which are termed diamagnetic.

`=>` `B = mu_0 (1+ chi)H`

`=mu_0mu_r H`

`=mu H`

where `mu_r= 1 + chi`, is a dimensionless quantity called the relative magnetic permeability of the substance. It is the analog of the dielectric constant in electrostatics. The magnetic permeability of the substance is `mu` and it has the same dimensions and units as `mu_0`.

`mu=mu_r mu_0=mu_0(1+chi)`