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arXiv 0911.2678cond-mat.mtrl-sci
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Pd薄膜的电驱动磁性

Electrically driven magnetism on a Pd thin film

Yang Sun, J. D. Burton, E. Y. Tsymbal

摘要:

使用第一性原理密度泛函计算,我们证明,铁磁性可以诱导和调制,否则顺磁性Pd金属薄膜表面通过施加外部电场。当自由电荷在Pd表面积聚或耗尽以屏蔽所施加的电场时,在表面态密度中存在相应的变化。这种变化可以足以使费米能级态密度满足Stoner准则,从而在临界施加电场Ec之上在表面处局部地驱动从顺磁状态到巡回铁磁状态的转变。此外,由于该转变的二阶性质,刚好在该转变之上的铁磁状态的表面磁化表现出对电场的实质依赖性,这是增强的磁电磁化率的结果。使用线性化的Stoner模型,我们解释了巡游铁磁性的发生,并证明在Pd表面上的磁矩遵循与我们的第一性原理计算一致的电场的平方根变化。

英文摘要:

Using first-principles density functional calculations we demonstrate that ferromagnetism can be induced and modulated on an otherwise paramagnetic Pd metal thin-film surface through application of an external electric field. As free charges are either accumulated or depleted at the Pd surface to screen the applied electric field there is a corresponding change in the surface density of states. This change can be made sufficient for the Fermi-level density of states to satisfy the Stoner criterion, driving a transition locally at the surface from a paramagnetic state to an itinerant ferromagnetic state above a critical applied electric field, Ec. Furthermore, due to the second-order nature of this transition, the surface magnetization of the ferromagnetic state just above the transition exhibits a substantial dependence on electric field, as the result of an enhanced magnetoelectric susceptibility. Using a linearized Stoner model we explain the occurrence of the itinerant ferromagnetism and demonstrate that the magnetic moment on the Pd surface follows a square-root variation with electric field consistent with our first-principles calculations.

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