The magnetization of a plate can be determined by applying the continuity conditions of the B and H fields at the interfaces of magnetic materials, while bearing in mind the relationship B = \mu_0(M + H). For a sphere, the same principles apply, although the calculations are more complex. NB! Do not forget that in soft ferromagnetic materials far from the saturation point, the relationship M=(\mu_r-1) H holds true, with \mu_r\gg 1.
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