Convergence of the volume-averaged demagnetising field $\langle H_z \rangle$ for uniformly magnetised bodies ($M_s$ = 800,000 A/m, magnetised along $z$). The analytical reference is $\langle H_z \rangle = -\mu_0 M_s^2 N_z$ where $N_z$ is the demagnetising factor.

All methods use the same underlying FEM mesh for the body region. The x-axis shows the number of nodes in the body (material region), giving a fair comparison between plain and shell meshes. Field values are volume-weighted averages using the FEM nodal volumes.