Magnetic Susceptibility

Magnetic Susceptibility

Magnetic Susceptibility

Magnetic Susceptibility

Magnetic susceptibility is the measure of magnetic properties of a material in the field of electromagnetism and is define whether a material is attracted into or repelled out of a magnetic field. Paramagnetic materials align with the applied field and are attracted to regions of greater magnetic field strength. Diamagnetic materials, on the other hand, are antialigned and are pushed away, toward regions of lower magnetic field strength.

Magnetic susceptibility is the ratio between magnetization M of the material in a magnetic field and the field intensity H.
M = ฯ‡·H
If the magnetic susceptibility is positive (๐œ’ > 0), then the material is paramagnetic or ferromagnetic or anti-ferromagnetic in nature. In this reference, the presence of the material results in the strengthening of the magnetic field. Magnetic susceptibility is high in value when it comes to Ferromagnets.
If the magnetic susceptibility is negative (๐œ’ < 0), then the material is diamagnetic in nature. This results in weakening of the magnetic field in presence of the material.
It is the ratio quantity of the same units, therefore it is dimensionless and also has no unit.

When a substance is subjected to magnetic field, polarization occurs and magnetic field ฮ”H is produced due to polarization. The total field strength is-
H = Ho + ฮ”H
where, Ho is applied magnetic field and ฮ”H is the field due to magnetic polarization. The relation is expressed as-
B = Ho + 4πI
where, B is magnetic induction and I is intensity of magnetization.
Dividing by Ho in the above equation we get-
B/Ho = 1 + 4π(I/Ho) = 4πk

where, B/Ho is magnetic permeability and I/Ho = k is magnetic susceptibility per unit volume and it is a measure of susceptibility of the substance to magnetic polarization. If k is divided by d, then-
k/d = ๐œ’
๐œ’ is magnetic susceptibility per gram.
๐œ’ x A = ๐œ’A is magnetic susceptibility per gram atom.
๐œ’ x M = ๐œ’M is magnetic susceptibility per gram mole.
When magnetic susceptibility is measured, ๐œ’M is susceptibility of paramagnetic substance plus susceptibility of diamagnetic substance and so correction of diamagnetic susceptibility is made and ๐œ’Mcorrection is obtained for paramagnetic susceptibility.
๐œ’Mcorrection = ๐œ’M − ๐œ’diamagnetic
Unit of ๐œ’M is m3kg-1

Magnetic Permeability is defined as the ratio of the magnetic flux density to the magnetic intensity. It is also called Permeability of Medium.
Magnetic permeability is the magnetization capability of the material that allows the magnetic line of force to pass through it. In other words, magnetic permeability supports the formation of a magnetic field. Magnetic permeability of material determines the amount of magnetic flux passing through it. It is denoted by the Greek letter ยต. ยต = B/Ho.
SI unit is Henry per meter (H/M) or newton per ampere square (N/A-2).

What causes susceptibility ?

Susceptibility is caused by interactions of electrons and nuclei with the externally applied magnetic field.

Determination of Magnetic Susceptibility by Gouy Method