Magnetic circuit designers often strive to get the maximum performance while also keep an eye on the circuit efficiency. With limited resources of rare earth materials and supply chain issues, magnetic circuit designers should evaluate the relationship between maximum performance and efficient use of rare materials to help alleviate the rare earth supply issues.

A good representation of magnetic circuit efficiency is the Figure of Merit defined by the magnetic energy in the functional volume as percentage of total energy in the permanent magnets. Using this definition, we plan to review the performance vs efficiency of the following devices:

• Magnetic field range and figure of merit of dipole structures (Halbach; diametrical ring; square cavity and yoked C-type dipole) and recommendation of efficient design types for the target magnetic field range

• Open circuit magnet for sensor applications

• Magnetic holding force devices

• Efficient axial field generation with ring type magnets

• Selection of steel to enhance performance with less permanent magnets

Balancing performance and efficiency are important especially for large quantity applications. By maximizing the efficiency of the circuit design, magnetic designers can do their part to help the rare supply issues.