Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions
Effect of spin-dependent screening on tunneling electroresistance and tunneling magnetoresistance in multiferroic tunnel junctions
复制标题
DOI：
10.1103/physrevb.81.104419
复制
发表时间：
2010-03
影响因子：
3.7
通讯作者：
M. Zhuravlev;S. Maekawa;E. Tsymbal
中科院分区：
文献类型：
--
作者：
M. Zhuravlev;S. Maekawa;E. Tsymbal
由于在常规隧道结中不存在的新功能，在（磁性）隧道结中使用铁电势垒作为功能材料最近引起了极大的关注。切换势垒的铁电极化会改变电导，从而产生隧穿电致电阻（TER）效应。在磁性隧道结中使用铁电势垒使其成为多铁性的，其中TER与隧穿磁致电阻（TMR）共存。在此，我们为多铁性隧道结（MFTJ）建立了一个简单模型，它由被铁电势垒层隔开的两个铁磁电极组成。该模型明确包含了与自旋相关的屏蔽势，从而扩展了先前针对铁电隧道结（FTJ）和MFTJ所开发的模型。我们的结果表明，与自旋相关的屏蔽效应可能相当大，并且可能对MFTJ中的TMR和TER有重大贡献。我们发现，与具有复合（铁电/介电）势垒层的FTJ类似，具有这种势垒的MFTJ中的TER显著增强，这表明对应于相反极化方向的态之间的电阻比可能高达\(10^{4}\)甚至更高。我们的结果表明，MFTJ中可能存在四种电阻态，它们的电阻有显著差异，并且有可能通过电场（通过势垒的铁电极化）和磁场（通过电极的磁化配置）来控制这些电阻。这些功能对于MFTJ的器件应用可能是有意义的。
Using a ferroelectric barrier as a functional material in a (magnetic) tunnel junction has recently attracted significant interest due to new functionalities not available in conventional tunnel junctions. Switching a ferroelectric polarization of the barrier alters conductance resulting in a tunneling electroresistance (TER) effect. Using a ferroelectric barrier in a magnetic tunnel junction makes it mutiferroic where TER coexists with tunneling magnetoresistance (TMR). Here we develop a simple model for a multiferroic tunnel junction (MFTJ) which consists of two ferromagnetic electrodes separated by a ferroelectric barrier layer. The model explicitly includes the spin-dependent screening potential and thus extends previously developed models for FTJs and MFTJs. Our results demonstrate that the effect of spin-dependent screening may be sizable and may provide significant contributions to TMR and TER in MFTJs. We find that, similar to FTJs with a composite (ferroelectric/dielectric) barrier layer, the TER in a MFTJ with such a barrier is dramatically enhanced indicating that the resistance ratio between the states corresponding to the opposite polarization orientations may be as high as ${10}^{4}$ and even higher. Our results demonstrate the possibility of four resistance states in MFTJs with a pronounced difference in resistance and a possibility to control these resistance by an electric field (through ferroelectric polarization of the barrier) and by a magnetic field (through magnetization configuration of the electrodes). These functionalities may be interesting to device applications of MFTJs.