Fabrication of Multipole Magnets with Enhanced Flux Density Using Anisotropic Bond Magnets for Miniature Optical Pickup Devices

Abstract

A prototype magnetizing fixture was designed based on magnetic flux patterns simulated using the three-dimensional finite-element method of the JMAG software package. Rectangular shaped anisotropic bond magnets with dimensions of 6×12×24 mm were magnetized to multipoles using the prototype and a pulse power source. The result was significant enhancement perpendicular to the surface component of magnetic flux density (Bz) in the hard-axis compared with Bz for conventional simple magnets, of which the front and back surfaces are magnetized to opposite polarities. Moreover, Bz reached the close value for the Halbach arrayed magnet, 0.24 T, with the same body size fabricated for the attainment target. The enhanced Bz was attributed to the cusp field formed by the flux from both side coils. Demonstrations indicated that the cusp field out of the easy-axis could be efficiently enhanced due to focusing of the flux.

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

“…8) However, our magnets still have an associated issue in that the intensity of B on one surface is unbalanced compared with that on the opposite surface. Moreover, we have not yet fully investigated the magnetic materials that are applicable to our process.…”