GFMC. Dpto. Física Aplicada III, Universidad Complutense de Madrid, Campus Moncloa., Madrid 28040, Spain.
Nat Commun. 2010 Sep 21;1:82. doi: 10.1038/ncomms1080.
In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, causing a null expectation value of the orbital magnetic moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment, and novel forms of ferromagnetic superexchange interaction unique to t(2g) electron systems have been theoretically predicted, although their experimental observation has remained elusive. In this paper, we report a new kind of Ti(3+) ferromagnetism at LaMnO(3)/SrTiO(3) epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role of orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and Mn moments by structural parameters is demonstrated. This result will provide important clues for understanding the effects of orbital degeneracy in superexchange coupling.
在电子-晶格耦合较强的系统中，如锰氧化物，轨道简并被解除，导致轨道磁矩的平均值为零。因此，磁结构由自旋-自旋超交换决定。然而，在钛酸盐中，由于 Jahn-Teller 变形较小，轨道简并可能允许轨道磁矩具有非零值，并且已经理论预测了独特的 t(2g)电子系统的新型铁磁超交换相互作用，尽管它们的实验观察仍然难以捉摸。在本文中，我们报告了 LaMnO(3)/SrTiO(3)外延界面上一种新的 Ti(3+)铁磁性。它源于向钛酸盐的空导带的电荷转移，并且具有自旋和轨道贡献，证明了轨道简并的作用。通过结构参数调节 Ti 和 Mn 磁矩的磁排列（铁磁或反铁磁）的可能性得到了证明。这一结果将为理解超交换耦合中轨道简并的影响提供重要线索。
