Multi-pole magnetization of NdFeB sintered magnets and thick films for magnetic micro-actuators

The multi-pole magnetization and magnetic structure modeling of flat miniature or thick film NdFeB magnets for actuator applications has systematically been studied. Multi-pole magnetization of sintered NdFeB magnets (thickness I and 2 mm) and of NdFeB thick films (thickness 100-800 mum) with a stripe pattern and a pole pitch of 2 or I turn is performed by pulse magnetization. The experimental conditions of the magnetization process are optimized to give a maximum flux density at the poles. The field distribution of the magnets is calculated using a boundary element method. The results are compared to surface flux densities determined experimentally with a Hall probe measuring device scanning the surface of the magnet. The magnetic field of a flat magnet is discussed as a function of the number of surface poles because only a multi-pole magnetization creates a sufficiently large field at the surface of the magnet plate. Since for a given pole pitch the flux density decreases with distance from the surface, the induction was optimized for a typical airgap distance for actuator applications of 0.25 mm. (C) 2004 Elsevier B.V. All rights reserved.