Improvement of the performance of permanent magnets through microstructure control

Abstract

We have been improving magnetic properties of permanent magnets through microstructure control. The main researches were (1) development of high-performance Fe-Cr-Co magnets by recrystallization texture and high coercivity Mn-Sn-Co-N-based alloys. We have been also improving magnetic properties in (2) rare earth magnets. Namely, a) Dy reduction in Nd-Fe-B sintered magnets, b) development of high performance Sm-Fe-N magnets and c) highly anisotropic Nd-Fe-B HDDR powders. In addition, we have studied about (3) the usage of hard magnetic materials for electromagnetic wave absorbers. Recently, the use of microwaves in the GHz range has increased because of the demand for large data transmission. However, the problem of electromagnetic interference (EMI) has become serious, and much attention has been paid to microwave absorption materials. We have investigated magnetic loss of permanent magnet materials at natural resonance frequency, and have succeeded in the development of new microwave absorbers using M-type (or W-type ferrite) and RE-Fe-B (RE: rare earth) compounds. In this article, researches described above, especially researches about microwave absorbers, are summarized.