To make the best use of a permanent magnet fully enough, an optimum design of magnetic circuit must be necessary, and one should be skilled with the characteristics etc. of designing of magnetic circuit technique and a permanent magnet for that.
Recently, the conditions of the design of magnetic circuit is getting much improved because of the advancement of the computer and the enhancement of software. On the contrary, however hardware and software of the design are being enhanced, it is not easy to design an optimum magnetic circuit without the adequate studying of a permanent magnet itself.
Therefore. let me introduce some examples of how to handle or how to evaluate a permanent magnet in this text.
Key-words: demagnetization, demagnetization curve, spontaneous magnetization, self demagnetization, operating point