Magnetic domains on unpolished and polished surfaces of titanium‐rich titanomagnetite
Magnetic domains on unpolished and polished surfaces of titanium‐rich titanomagnetite
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富钛钛磁铁矿未抛光和抛光表面的磁畴
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发表时间：
1988
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通讯作者：
C. A. Lawson
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作者：
B. Moskowitz;S. Halgedahl;C. A. Lawson
采用干苦味法和扫描电子显微镜 (SEM) 研究了合成铝镁钛富钛磁铁矿 (AMTM60) 未抛光和抛光表面上的磁畴。 SEM 的高放大倍率和卓越的分辨率可以轻松测量特征域特征，包括域壁宽度。 SEM 的大景深还允许研究未抛光样品表面上的域图案。结果发现，在未抛光、未抛光但酸蚀刻和离子抛光的表面上观察到类似的域结构。然而，即使在未抛光的表面上，AMTM60 中的磁畴样式也与基于其立方磁晶各向异性的该材料预期的磁畴样式不同。在未抛光表面上常见的特征包括（1）紧密间隔的条纹域，（2）正弦波壁，（3）成排的圆形尖峰域，以及（4）复杂的波状壁图案，由波状和分支壁包围的星状特征组成。所有这些特征都对应于单轴材料中发现的磁畴结构，其各向异性Ku和饱和磁化强度Ms满足条件2πMs2/Ku<1。 AMTM60 中单轴各向异性的来源很可能是残余应力。 AMTM60 中交换常数和各向异性常数的定量估计是通过使用正弦波壁理论模型对域模式进行分析而获得的。此外，正如理论预测的那样，随着域图案的几何复杂性从简单的条纹域增加到复杂的波状壁域，以响应局部残余应力的降低，壁宽度增加，各向异性减小。最后，观察到抛光和未抛光表面上的域样式之间存在重要差异。仅在离子抛光表面上，许多区域表现出“斑驳”外观，其中畴样式突然改变或畴壁在斑块边缘完全消失，这表明机械抛光产生的应力可能没有通过离子抛光完全或均匀地消除。因此，尚不确定富钛钛磁铁矿中有多少本征域结构能够在机械抛光中幸存下来。
Magnetic domains on unpolished and polished surfaces of synthetic aluminium-magnesium titanium-rich titanomagnetite (AMTM60) have been investigated with the dried Bitter method and scanning electron microscopy (SEM). The high magnification and superior resolution of the SEM afforded easy measurements of characteristic domain features, including domain wall widths. The large depth of field of the SEM also allowed domain patterns on unpolished sample surfaces to be studied. It was found that analogous domain structures were observed on unpolished, unpolished but acid-etched, and ionically polished surfaces. However, even on unpolished surfaces, the domain style in AMTM60 was different from that expected for this material based on its cubic magnetocrystalline anisotropy. Features commonly observed on unpolished surfaces included (1) closely spaced stripe domains, (2) sinusoidally wavy walls, (3) rows of circular spike domains, and (4) complicated wavy wall patterns consisting of star like features enclosed by undulating and branching walls. All these features corresponded to domain structures found in uniaxial materials whose anisotropy Ku and saturation magnetization Ms satisfy the condition 2πMs2/Ku<1. The source of the uniaxial anisotropy in AMTM60 was most likely due to residual stress. Quantitative estimates of the exchange and anisotropy constants in AMTM60 were obtained from analysis of domain patterns using a theoretical model for sinusiodally wavy walls. Furthermore, as predicted by theory, wall widths increased and anisotropy decreased as the geometric complexity of the domain pattern increased from simple stripe domains to complicated wavy wall domains in response to a decrease in local residual stresses. Finally, it was observed that there was an important difference between domain style on polished and unpolished surfaces. On ionically polished surfaces only, many regions exhibited a “patchy” appearance, in which the domain style changed abruptly or in which domain walls disappeared completely at the edge of the patch and suggested that stresses produced by mechanical polishing may not have been removed completely or uniformly by ionic polishing. Consequently, it is uncertain how much of the intrinsic domain structure in titanium-rich titanomagnetites survives mechanical polishing.