Development of Zn-bonded Sm-Fe-N permanent magnet and magnetic powders with high magnetic coercivity

我们尝试使用具有高磁各向异性和高居里温度的Sm-Fe-N化合物在高温下建立具有高矫顽力的永久粉末。本文的主要工作是通过气相沉积和电化学沉积的方法，在Sm-Fe-N化合物粉末表面涂覆锌膜，以提高其磁性。我们已获得如下资料。以钐铁氮和锌粉为原料，确定了等离子烧结法制备高矫顽力材料的温度、压力和时间条件。结果表明，在420℃、5000 kg/cm^2、5min条件下，矫顽力达到20kOe。结果表明，与普通烧结方法相比，等离子烧结是在短时间、低压力下建立高矫顽力的有力工具。我们采用气相沉积和电化学沉积的方法对平均粒径为20mum（粗粉）和3mum（细粉）的Sm-Fe-N粉末进行了镀锌处理，然后采用等离子烧结的方法进行了烧结。结果表明，涂锌可以提高粗粉的矫顽力，但对细粉没有改善作用。研究表明，开发新的镀锌方法是必要的。我们成功地用高分辨率透射电镜观察了包括Mn在内的具有高矫顽力的Sm-Fe-N粉末，发现磁畴壁的钉钉是由直径约为10 nm的细晶晶体产生的。

We have tried to establish permanent powders with high magnetic coercivity at high temperatures by using the Sm-Fe-N compound, which has high magnetic anisotropy and high Curie tepmperature. In particular, the present work is directed toward the development of the magnetic coercivity by coating the powders of Sm-Fe-N compound with zinc films, by using vapor deposition and electro-chemical deposition. We have obtained as follows.1.We have determined optical conditions of temperature, pressure and time to prepare the high-coercivity material by the plasma sintering method, by using starting materials of the Sm-Fe-N and zinc powders. As a result we obtained the maximum coercivity of 20kOe at 420ﾟC,5,000kg/cm^2, and for 5 min. The result shows that the plasma sintering is a powerful tool to establish high coercivity in a short time and at a low pressure, compared with ordinary sintering methods.2.We have carried out zinc-coating the Sm-Fe-N powders with an average sizes of 20mum (rough powders) and 3mum (fine powders), by using vapor deposition and electro-chemical deposition, and then sintered by the plasma sintering method. As a result we have obtained the improvement of the magnetic coercivity by zinc coating for the rough powders, but no improvement for the fine powders. It is concluded that the development of new methods of zinc coating is necessary.3.We have succeeded in high-resolution transmission electron microscopy observations of Sm-Fe-N powders including Mn, which are expected to be high coercivity of pinning-type, and found that the pinning of magnetic domain walls is produced by fine-grained crystals with about 10 nm in diameter.