電子線ホログラフィーによるNd-Fe-B系ナノコンポジット磁石の磁区構造解析

抄録

  Magnetic flux distribution in Nd-Fe-B based nanocomposite magnets was investigated at nanometer scale by electron holography. Both Nd_4.5Fe₇₇B_18.5 and Nd-Fe-B-Ti-C, the latter of which was newly developed and commercialized under tradename of SPRAX, are found to consist of hard and soft magnetic grains of 10~30 nm in diameter. Through the comparison of reconstructed phase images of Nd_4.5Fe₇₇B_18.5 and Nd-Fe-B-Ti-C, it is found that the lines of magnetic flux of Nd-Fe-B-Ti-C fluctuate more largely than Nd_4.5Fe₇₇B_18.5 in both demagnetized and remanent states. The fluctuation in the distribution of lines of magnetic flux is considered to result from the randomness in the crystal orientation of the hard magnetic grains with high anisotropy. It is also pointed out that the fluctuated distribution of lines of magnetic flux is consistent with the high coercivity and high maximum energy product of Nd-Fe-B-Ti-C.