低维磁性材料的磁性相变

Magnetic transformation of low dimensional magnetic materials

对由分子束外延MBE法制备的[α-Fe/Au]多层薄膜和化学共沉淀法制备的Fe3O4超细微粒进行了温度为77～900K的磁化-温度曲线的测试，首次发现影响居里温度瓦的因素，并确定了样品的临界指数声和转变临界指数A的值。测试显示：在[α-Fe/Au]层薄膜中，居里温度瓦随Fe层膜厚变薄而降低；在Fe3O4超细微粒中，居里温度瓦随微粒直径减少而降低。这一结果表明，如果能控制磁性薄膜的厚度和超微粒的尺寸，就能控制磁性体的居里温度瓦，这在低维磁性材料的应用方面有很大的实际价值。

In this work, the multilayers of [α-Fe/Au] are prepared by epitaxial growth method and the ultra-fine particles of Fe3O4 are prepared by co-precipitation method. The plots of magnetization at the temperature from 77K to 900K of both the two kinds of samples have been investigated. From the plots, we have estimated the value of critical exponent β and shift critical exponent λ It the first time that have reported the factor on which Tc depends and have discovered that the value of Te decreases with the decreases of the thickness of Fe in the mulfilayers.The phenomenon can be found in the Fe3O4 particles.The results of this report show that if the thickness of multilayers and the diameter of the ultra-fine particles can be controlled, Tc could be controlled in the other word. So this will be applied into in the low dimensional magnetic materials.