Sub-Millimeter Pitch Multipole Magnetization in a Sintered Nd-Fe-B Magnet Utilizing Laser Heating

Sub-millimeter pitch, multipole magnetization is obtained in a sub-millimeter-thick, sintered, Nd-Fe-B magnet. Regions of a perpendicularly magnetized part are heated by a scanned laser beam. The heated regions with lower coercivity are reverse-magnetized by the leakage flux from adjacent unheated areas. A high aspect ratio of magnetized width to thickness is achieved by the use of heat insulating slits. The slit depth and laser scanning conditions were determined by simulating the temperature distribution in the magnet. A 500 μm thick multipole magnet with a 650 μm pitch had a vertical magnetic field of 0.48 T (p-p) at a distance of 100 μm from the surface, in close agreement with the simulation.