Demagnetisation correction

For many magnetic materials the demagnetisation correction for susceptibility is not important since x 1 which implies Xint Xext- When the susceptibility is high, the demagnetisation correction adopts its significance. 

The demagnetisation correction is applicable only to the volume susceptibility. This requires an accurate determination of the sample volume, which may not be trivial. Normally the amount of the sample is determined by weighing and it refers to the sample mass. The determination of the volume is less accurate and more complex for powders. 

Different experimental techniques, depending on whether they register the magnetic response in static or alternating fields, yield different types of magnetic susceptibility. In certain situations a correction to the demagnetisation effects is necessary. 

Strong diamagnetic materials exhibit a volume susceptibility close to the limit of x = — 1 (dimensionless). These obey perfect diamagnetic screening due to a superconducting current and in fact they are superconductors. Thus the measurement of magnetic susceptibility serves as a convenient and fast identification of superconductivity, even for powder materials (the Meissner effect). However, due to the considerable susceptibility value, the demagnetisation effect becomes substantial and thus a correct determination of... 

---