Control of Spin-Density-Wave Magnetic Structures using Interface Effects

铬是一种典型的具有“自旋-密度-波”磁性结构的材料，它的自旋结构(磁结构)是利用界面效应控制的。块体铬具有体心立方(Bcc)结构，在311K以下表现为自旋密度波反铁磁结构，自旋磁矩在每个bcc(001)面上平行排列，在相邻bcc(001)面间反平行，并以6~8 nm的周期正弦调制。采用超高真空沉积法制备了具有X元素单原子层周期性镶嵌在铬膜中的外延Cr/X多层膜，并用中子衍射和穆斯堡尔谱对其自旋结构进行了研究。研究发现，在多层膜中出现了体相中没有观察到的新的自旋结构，这是由于界面效应在嵌入的X原子处的反节点或自旋密度波调制节点的钉扎所致。自旋结构取决于插入元件的种类，因此可以通过选择反元件来控制。研究还发现，即使铬层厚度相同，bcc(001)取向的Cr/X多层膜和bcc(011)取向的多层膜的自旋结构也有很大不同。这些结果被“嵌套效应”和“界面效应”的竞争所解释。通过这种方法，证明了可以利用界面效应来控制自旋密度波磁结构。

The spin structure (magnetic structure) of Cr, which is a typical material having a "spin-density-wave" magnetic structure, was controlled using interface effects. Bulk Cr has a body-centered cubic (bcc) structure and, below the magnetic transition temperature of 311 K, shows a spin-density-wave antiferromagnetic structure, where the spin magnetic moments align parallel in each bcc (001) plane and antiparallel between adjacent bcc (001) planes and modulate sinusoidally with a period of 6 to 8 nm. Epitaxial Cr/X multilayers, which have a structure where monatomic layers of element X are periodically embedded in a Cr film, were grown by ultrahigh-vacuum deposition and the spin structures were examined by neutron diffraction and Mossbauer spectroscopy. It was found that novel spin structures, which are not observed in bulk Cr, appear in the multilayers due to the pinning of antinodes or nodes of spin-density-wave modulation at the embedded X atoms through interface effects. The spin structures were dependent on the sort of the inserted element and thus can be controlled by selecting the counter element. It was also found that the spin structures of bcc (001)-oriented Cr/X multilayers and those of bcc (011)-oriented multilayers are quite different even when the Cr layer thickness is the same. These results are interpreted by the competition between the "nesting effect" and the interface effect. In this way, it was demonstrated that spin-density-wave magnetic structures can be controlled by making use of the interface effects.