Yasushi Nakahata

Magnetization Process Simulation of Anisotropic Permanent Magnets by Using the Three-Dimensional VMSW Method

This paper presents a 3-D variable magnetization and Stoner-Wohlfarth (VMSW) method developed by expanding the conventional 2D-VMSW model. The 3-D VMSW method enables us to estimate distributions of remanent magnetization in magnetized permanent magnets in three dimensions.

The Precise Measurements of Coercivity Fields of Nd-Fe Ferro-Magnets in Pulsed High Magnetic Fields up to 20T

The measurements of the coercive force (Hc) of magnets are very difficult to determine as a function of the true effective fields in samples with arbitrary shapes. In this study, we tried to obtain the exact coercive force, M-H curve in high and high pulsed magnetic fields up to 20T by using a double-core pick-up. The values of Hc were found over-estimated more than 20% for the Nd-Fe magnets in comparison with those announced by the company, which coincided well with the numerical simulations by using JMAG. The two samples cut along easy and hard axis showed the same saturation magnetizations, reflected by the isotropic microstructure of the raw material.

Construction of the Pulsed High Magnetic Field Generator up to 33T and the Enhancements of the Magnetic Coercivity in High Fields

M-Heff full curves up to 19T for the permanent magnets composed of Nd-Fe-B were very precisely observed by using specially designed magnetizer. The pulsed magnetic field directions were safely reversed with the same coil-end to ground side of coil positive and negative field directions. The coercivity enhancements were observed by 15% in high pulsed field applications.

Precise measurement of magnetization characteristics in high pulsed field

Permanent magnets, especially Nd-Fe-B magnets, are very important engineering elements that are widely used in many applications. The detailed design of electrical and electronic equipment using permanent magnets requires the precise measurement of magnetization characteristics. High pulsed magnetic fields can be used to measure the magnetization characteristics of permanent magnets in the easy and hard magnetization directions. Errors influencing the measurements stem from the relationship between the tested material, pick-up sensor configuration, and excitation coil. We present an analysis of the effect of the sensor construction on the accuracy of the measurements of the material’s magnetic properties. We investigated the coaxial and series types sensor configurations.