The determination of the demagnetization factor resulting from shape anisotropy in ferrite magnets
The energy equation which yields the expression,H ci=0.48[2K 1/M s−4πM s ], for the intrinsic coercive force of BaFe12O19 has been used as the basis for numerous investigations. There is reason to believe, however, that the term, 4π, in this expression should be replaced by 2π. To settle this question, the energy equation is resolved to obtain expressions for both the easy and hard directions of magnetization. The resultant equations are used to establish a procedure for the determination of the demagnetization factor resulting from shape anisotropy in ferrite magnets. A related method is introduced to calculate the saturation magnetization of ferrite magnets. It is demonstrated thatM s values derived by means of this procedure deviate from single-crystal values by ±4 parts per thousand, maximum. This method uses magnetic measurements made in the field,H a=H A/2 for both the hard and easy directions of magnetization. The evidence obtained leads to the conclusion that,H ci=0.48[2K 1/M s−2πM sc], for the Stoner-Wohlfarth spherical model.
