The output and optimum design of permanent magnets subjected to demagnetizing forces

THE recent development of new permanent-magnet alloys having a high available energy has extended considerably the field of permanent-magnet applications. Prominent among these new materials is the group of aluminum-nickel-iron alloys which has been given the name “Alnico”. These alloys are characterized by coercive forces of 400 to 700 oersteds, residual inductions of 6,500 to 7,800 gausses, and available energy values ranging from 1.3 × 10⁶/8π to 1.7 × 10⁶/8π ergs. Corresponding values of these quantities for three other well-known magnet materials are given in table I, and characteristic curves for these materials are shown in figure 1.