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**Thermal Behavior and Demagnetizing Factor of Nd-Fe-B & other Magnets:****Disadvantage and Advantage in Their Applications**(By Christina Chen & Pengpeng Yi)**The Relationship of Permeance Coefficient B/H, Load line, Demagnetizing Factor, and L/D****In actual magnetic devices, the demagnetizing field depends on the demagnetizing factor N, which in turn depends on the geometry of the magnets and their permeability.**

**Theoretically the demagnetizing factor can be calculated precisely only for the case of an ellipsoidal sample; for other regular geometries, it must be determined experimentally or calculated numerically subject to certain assumptions. Errors are inevitable for such calculations. There are various methods to determine the demagnetizing factors, which can be found in many references.**

**A convenient method has been used by many in the industry, which is described in Rollin J Parker’s book of Advances in Permanent Magnetism. Parker summarized the relationship of permeance coefficients and various magnet shapes, such as rings, rectangles, which are plotted in the 4 figures below. The formulas for calculating the plots are listed in the figures respectively.**