Division of Superconductivity and Magnetism, University of Leipzig, D-04103 Leipzig, Germany.
Nano Lett. 2012 Aug 8;12(8):4276-81. doi: 10.1021/nl301963a. Epub 2012 Jul 13.
The study of spatially confined complex oxides is of wide interest, since correlated electrons at interfaces might form exotic phases. Here La(0.7)Sr(0.3)MnO(3)/SrRuO(3) superlattices with coherently grown interfaces were studied by structural techniques, magnetization, and magnetotransport measurements. Magnetization measurements showed that ferromagnetic order in ultrathin La(0.7)Sr(0.3)MnO(3) layers is stabilized in the superlattices down to layer thicknesses of at least two unit cells. This stabilization is destroyed, if the ferromagnetic layers are separated by two unit cell thick SrTiO(3) layers. The resistivity of the superlattices showed metallic behavior and was dominated by the conducting SrRuO(3) layers, the off-diagonal resistivity showed an anomalous Hall effect from both SrRuO(3) and La(0.7)Sr(0.3)MnO(3) layers. This shows that the La(0.7)Sr(0.3)MnO(3) layers are not only ferromagnetic but also highly conducting; probably a conducting hole gas is induced at the interfaces that stabilizes the ferromagnetic order. This result opens up an alternative route for the fabrication of two-dimensional systems with long-range ferromagnetic order.
对空间限制的复杂氧化物的研究很有意义，因为界面处的相关电子可能会形成奇特的相。在这里，通过结构技术、磁化和磁输运测量研究了具有相干生长界面的 La(0.7)Sr(0.3)MnO(3)/SrRuO(3)超晶格。磁化测量表明，在超晶格中，超薄 La(0.7)Sr(0.3)MnO(3)层中的铁磁有序在至少两个单元胞厚度下稳定存在。如果铁磁层被两个单元胞厚的 SrTiO(3)层隔开，则这种稳定化会被破坏。超晶格的电阻率表现出金属行为，主要由导电 SrRuO(3)层决定，非对角电阻率显示出来自 SrRuO(3)和 La(0.7)Sr(0.3)MnO(3)层的反常霍尔效应。这表明 La(0.7)Sr(0.3)MnO(3)层不仅是铁磁的，而且也是高导电性的；可能在界面处诱导了一个导电的空穴气体，从而稳定了铁磁序。这一结果为具有长程铁磁序的二维系统的制造开辟了一条替代途径。
