material mixture has a coercivity such that remagnetization is not possible with the magnetic fields usually generated powdered materials of the fe 2 o 3 ferrite or samarium cobalt sm 2 co 5 or sm 2 co 7 type are suitable another means of neutralization consists in providing a compound which degrades the ferromagnetic band 22 in the composition of the colloidal gel 8 39 even at a low concentration the compound will attack the band 22 which triggers a recrystallization nucleus of the amorphous ferromagnetic material the compound will also act by degrading the surface of the ferromagnetic band as the properties of the band depend on an optimum ratio between the length and the square root of the area of the transverse section of the band alteration by scouring will result in the neutralization of the band this will be sufficient to entail the irreversible loss of the magnetic characteristics of the magnetic material a strong acid such as nitric acid or hydrofluoric acid is suitable mechanical action allows it to be diffused above the band 22 in the same manner and using the same processes as those described above thus whatever the type of antitheft influence means used the neutralization can be carried out by provoking by means of mechanical action applied to the outside of the label and transferred inside it the spreading of a substance with particular properties thereby to closely associate the substance with the influence means more specifically the mechanical pressure action p causing spreading of the substance on the influence means and annihilation of its effects can be applied deliberately using a finger 23 but in particular in.