The " volume magnetic susceptibility ", represented by the symbol \ chi _ v ( often simply \ chi, sometimes \ chi _ m magnetic, to distinguish from the electric susceptibility ), is defined in the International System of Units in other systems there may be additional constants by the following relationship:
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For example, when a material is put in an electric field "'E "', which ramps up from zero to a finite value, the material's electronic and ionic positions slightly shift . This changes "'P "', and the result is electric susceptibility ( and hence permittivity ).
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More formally, it states that the coefficient of the second order electric susceptibility response ( \ chi _ { \ text { 2 } } ) is proportional to the product of the first-order susceptibilities ( \ chi _ { \ text { 1 } } ) at the three frequencies which \ chi _ { \ text { 2 } } is dependent upon . { { cite book
