关于图的平方根的一个注记

The Origin of the Magnetocrystalline Anisotropy in PrCo 5

给出了一个以图的边数来判断一个图是否存在平方根的一个必要条件：对于图Ｇ（Ｖ，Ｅ），若｜Ｅ｜＜２｜Ｖ｜－３，则此图无平方根．

The origin of the magnetocrystalline Anisotropy in PrCo 5 is studied based on the single ion model.The change of the Anistropy with temperature is caculated.The result shows that the crystall field and the shield factor have greater influence on the anisotropy,however,the exchange of interaction has less.The result of theory analysis also explains the phenomenon that PrCo 5 changes to the C axis magnetization from C awl plane magnetization.