Planar Bonded Magnets with 52% Enhanced Stray Magnetic Flux Density and the Same Polarity at Both Surfaces via Homopolar Magnetization

Abstract

An optimized homopolar magnetizing fixture consisting of four magnetic pole pieces was developed with the aim of achieving a focused magnetic flux on the surfaces of Nd-Fe-B alloy-based permanent magnets, and thus enhancing the magnetic flux density. In this fixture, only the transverse pieces involved coils providing the same magnetic poles in response to a pulsed current. Rectangular anisotropic and isotropic bonded magnets as well as sintered magnets, having dimensions of 6 mm © 12 mm © 24 mm or 6 mm © 12 mm © 16 mm, were magnetized to multipoles using a prototype fixture in conjunction with a pulsed power source. As a result, the magnetic flux density perpendicular to the surface (B z ) was increased by 52% relative to that of conventional simple magnets containing the same volume of magnetic compound, with the front and back surfaces magnetized to opposite polarities. In addition, the B z polarities of both the front and back sides of the magnet were determined to correspond to N-poles. The distribution pattern of B z led us to conclude that the enhanced B z and the equal polarity on both sides can both be attributed to the cusp field resulting from the flux generated by the transverse coils of the magnetizing fixture.