Nat Mater. 2012 Feb 26;11(4):289-93. doi: 10.1038/nmat3254.
Spin-polarized transport in ferromagnetic tunnel junctions, characterized by tunnel magnetoresistance, has already been proven to have great potential for application in the field of spintronics and in magnetic random access memories. Until recently, in such a junction the insulating barrier played only a passive role, namely to facilitate electron tunnelling between the ferromagnetic electrodes. However, new possibilities emerged when ferroelectric materials were used for the insulating barrier, as these possess a permanent dielectric polarization switchable between two stable states. Adding to the two different magnetization alignments of the electrode, four non-volatile states are therefore possible in such multiferroic tunnel junctions. Here, we show that owing to the coupling between magnetization and ferroelectric polarization at the interface between the electrode and barrier of a multiferroic tunnel junction, the spin polarization of the tunnelling electrons can be reversibly and remanently inverted by switching the ferroelectric polarization of the barrier. Selecting the spin direction of the tunnelling electrons by short electric pulses in the nanosecond range rather than by an applied magnetic field enables new possibilities for spin control in spintronic devices.
铁磁隧道结中的自旋极化输运，其特征为隧道磁电阻，已经被证明在自旋电子学和磁随机存取存储器领域具有巨大的应用潜力。直到最近，在这种结中，绝缘势垒仅起着被动的作用，即促进铁磁电极之间的电子隧穿。然而，当使用铁电材料作为绝缘势垒时，出现了新的可能性，因为这些材料具有可在两个稳定状态之间切换的永久介电极化。因此，在这种多铁隧道结中，除了电极的两个不同磁化排列之外，还存在四个非易失性状态。在这里，我们表明，由于多铁隧道结的电极和势垒之间界面处的磁化和铁电极化之间的耦合，通过切换势垒的铁电极化，可以可逆和永久地反转隧穿电子的自旋极化。通过纳秒范围内的短电脉冲而不是通过外加磁场来选择隧穿电子的自旋方向，为自旋电子器件中的自旋控制提供了新的可能性。
