Pioneering work of the mechanism elucidation of a new type ferromagnet Ca(La)B_6 by ESR.

关于一种新型铁磁体Ca(La)B_6的令人惊讶的论文发表在2000年2月的《自然》杂志上。从那时起，出现了许多理论论文，但没有出现一篇实验论文。原因是样品制备非常困难，因为熔点非常高（- 2500℃），液相和气相共存。为克服上述问题，采用铝助熔剂法制备了Ca(La)B_6单晶。我们在日本首次发现了Ca(La)B_6的铁磁性。此外，我们还利用电子自旋共振（ESR）解释了铁磁性的形成机理。也就是说，由于铁磁性的自旋在各向异性场的作用下被强烈地强迫留在磁盘平面上。结果表明，Ca(La)B_6中的自旋仅存在于约1.5 μm厚的表面层内，具有较强的易平面型表面磁各向异性。

The surprising paper of a new-type of ferromagnet Ca(La)B_6 was reported in "Nature" at February,2000. There were many theoretical papers appeared since then, but an experimental paper was not appeared. The reason was that the sample preparation was very difficult, because the melting point is very high (-2,500℃), and the liquid phase and the gas phase are co-existing. We are overcoming the above problems, we succeeded the single crystals of Ca(La)B_6 by Aluminum-flux method. We found out, first time, the ferromagnetism of Ca(La)B_6 in Japan. Moreover, we elucidate the mechanism of the ferromagnetism by electron spin resonance (ESR). That is, the spins owing to ferromagnetism are strongly forced to stay in the disk plane by an anisotropy field. We conclude that spins in Ca(La)B_6 exist only within the surface layer of approximately 1.5 μm thick, and they feel strong surface magnetic anisotropy of an easy plane type.