材料期刊网

用电子衍射方法和Lorentz电子显微术观察了非晶态Gd-Co合金磁膜结构和磁畴的变化。薄膜在10~(-2)mmHg的低真空下作了为期二周的室温处理,也在5×10~(-7)mmHg的高真空下加热。发现低真空下作室温处理和高真空下加热都能使薄膜中发生相分离,而且薄膜的衍射强度峰形和磁畴图象均随之发生变化,Gd与Co原子间最近邻配位数明显下降,与此同时磁畴图象中的磁泡显著减少甚至消失,出现平面畴。这再次证实了非晶态Gd-Co合金磁膜各向异性与Gd,Co原子间最近邻配位数有一定联系,而且配位数能直观反映在衍射峰形上。 加热至350℃时Co首先结晶,其主要组成为α-Co,并有少量β-Co。随着温度继续上升α-Co逐渐转变为β-Co。即使加热至950℃亦未见Co氧化,而Gd在晶化之前就严重氧化。在晶化的全过程中均未发现Gd-Co台金和金属Gd的痕迹。 本文还给出了磁畴图象随温度的变化,并讨论了薄膜中的相分离和短程有序状态对磁各向异性的影响。

Changes in the structure and the magnetic domain patterns in amorphous Gd-Co alloy films after annealing at room temperature in a low vacuum of 10~(-2) mmHg for 2 weeks as well as heating in a high vacuum of 5×10~(-7) mmHg were investigated by electron diffraction and Lorentz electron microscopy. It was found that the phase separation could be achieved either by annealing at room temperature in low vacuum or by heating in high vacuum.The diffraction intensity profiles of the films and their magnetic domain patterns were changed as a result of phase separation. The nearest neighbor coordination number between Gd and Co atoms was obviously decreased, meanwhile the magnetic bubbles in the domain patterns were apparently decreased or even disappeared, resulting in the fact that the in-plane domain appeared. This probes once again that the magnetic anisotropy in amorphous Gd-Co alloy films is definitely related to the nearest neighbor coordination number between Gd and Co atoms and that the latter may be intuitively shown in the electron diffraction intensity profile.It was also found that during heating at 350℃, Co crystallized first with α-Co as its main product and β-Co the subordinate. The α-Co gradually transformed into β-Co with the increase of temperature. The oxidation of Co had not been observed even at 950℃ while Gd was oxidized seriously before its crystallization.No trace of Gd-Co alloy or metal Gd could be found in the whole process of crystallization.The change of the magnetic domain patterns with the heating temperature was shown in the present paper. The influence of both the phase separation and the degree of short range order on the magnetic anisotropy in films was discussed.