Magnetic SusceptibilityPublished on 24/2/2012 and last updated on 27/7/2018
Now, Magnetic susceptibility can be simply defined as the measurement of the extent to which a substance can be magnetised by applying a peripheral magnetic field. It is denoted by (from the Greek letter chi). It can be measured as M - magnetisation of the material H - Applied peripheral magnetic field strength Magnetic susceptibility is actually caused by the reciprocal action of electrons and nuclei by the application of peripheral magnetic field. That is, a c takes place inside it that will either opposes or intensify the applied peripheral field. If it opposes the applied magnetic field, the result will be diamagnetism.
If it intensifies the field (the electrons and nuclei which rotates in the same direction of magnetic field) it results in paramagnetic or ferromagnetic or super magnetism depending on the degree of intensification. The range of the value of magnetic susceptibility () of different magnetic substances is
- Diamagnetic substances : < 0
- Paramagnetic substances : 1 > > 0
- Super paramagnetic and ferromagnetic substances : >> 1
Now, consider a material having magnetisation M which is placed under a peripheral magnetic field of B0 and the magnetic permeability of free space is µ0. Then, the total magnetic field in the material after applying peripheral magnetic field is given by When the internal magnetic field of the material is considered, µ0 can be substituted by µ which is given by µ = Km µ0. Where, Km is relative permeability. If the material does not produce any internal magnetism with applied magnetic field, then the value of Km will be equal to 1. When Km>1, due to the application of a peripheral magnetic field the material is magnetised. The can be related with Km, i.e is defined as how much value the relative permeability differs from one. m and Km will give same information. Both quantities are dimensionless.