Magnetic susceptibility is the scale of magnetization of a substance in reaction to an functional magnetic field. Magnetic susceptibility (Xm) is a property which determines how easily and how strongly a specimen can be magnetized.
Susceptibility of a magnetic material is defined as the ratio of intensity of magnetization I induced in the material to the magnetizing field H in which the material is placed.
Thus Xm = I/H
Since I and H are of the same dimensions, Xm has no unit and is dimensionless.