Magnetic tunnel junctions with perpendular anisotropy

具有垂直各向异性的磁隧道结

• 批准号: 188402195
• 负责人: Professor Dr. Günter Reiss
• 金额: --
• 依托单位: Arbeitsgruppe Dünne Schichten und Physik der Nanostrukturen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/188402195?language=en
• 关键词: Magnetic; tunnel; junctions; perpendular; anisotropy

Magnetic tunnel junctions with perpendicular anisotropy show extremely small current densities for spin transfer torque switching (STT). In addition, the temperature, the electric field and the film thickness have a strong impact on the anisotropy and the switching of the magnetization. In particular the impact of the electric field, which is not yet well understood, opens paths towards devices with extremely small power consumption. Using tunnel junctions with CoFeB electrodes and MgO barriers, we have found a switching current density down to 100 kA/cm². Apparently unphysical values (< 10 A/cm²) can be realized as well. For the conditions that are necessary to obtain these values, however, it turned out that all three factors (spin polarized current density, temperature and electric field) modify the magnetic properties and thereby the switching behaviour.This is the motivation for the application for continuation of funding: in the further course of the project, we want to realise the three effects in pure form by systematically varying the thickness of the tunnel barrier and that of one of the electrodes made from Co, Fe and CoFe(B) and a non-magnetic counter electrode. In particular the impact of the electric field will be studied by using thick barriers which allow only small tunnel currents and prevent heating. We plan to apply the magnetooptical Kerr Effect and the Circular and Linear X-ray Dichroism at the synchrotron to study the effect in detail. We hope for findings about the question, in how far a change of the electron density and/or an impact on the orbital moments at the interface ferromagnet/insulator are responsible for the effect. Using these inputs, we then want to realise complete tunnel junctions with a size smaller than 200nm that allow to combine all three effects and thereby to achieve high data stability and low switching power (fJ-range).In a second PhD thesis, we plan to increase the so far very small number of materials that allow studying these effects. In particular ferro- and ferrimagnetic materials with small electron density are in the focus of the project. We target at semiconducting ferrites and the system Mn-Ge. For both material classes, we already achieved preliminary results. Both material classes are very promising, since the ferrites are semiconducting and for the Mn-Ge system a perpendicular anisotropy and a low metallic electron density can be expected. For these materials, we plan to first conduct basic studies of the preparation of very thin epitaxial films and of the impact of an electric field on the magnetic properties. The latter should be studied by the Hall Effect and the Anomalous Hall Effect. These studies should be followed by the realisation of magnetic tunnel junctions that allow for electric field effects at film thicknesses larger than for the CoFeB system.

具有垂直各向异性的磁性隧道结显示出极小的自旋转移矩开关（STT）电流密度。此外，温度、电场和薄膜厚度对磁化强度的各向异性和开关都有很大的影响。特别是电场的影响，这还没有得到很好的理解，开辟了通往具有极小功耗的设备的道路。使用具有CoFeB电极和MgO势垒的隧道结，我们发现开关电流密度低至100 kA/cm²。显然，非物理值（< 10 A/cm²）也可以实现。然而，对于获得这些值所必需的条件，结果表明，所有三个因素（自旋极化电流密度、温度和电场）改变磁性，从而改变开关行为。这是申请继续资助的动机：在该项目的进一步过程中，我们希望通过系统地改变隧道势垒的厚度和由Co制成的电极之一的厚度来实现纯形式的三种效应，Fe和CoFe（B）以及非磁性对电极。特别是电场的影响，将通过使用厚的障碍，只允许小的隧道电流和防止加热进行研究。我们计划在同步加速器上应用磁光克尔效应和圆、线X射线二向色性来详细研究这种效应。我们希望发现的问题，在多远的电子密度的变化和/或在界面铁磁体/绝缘体的轨道时刻的影响负责的效果。使用这些输入，我们希望实现尺寸小于200 nm的完整隧道结，允许联合收割机结合所有三种效应，从而实现高数据稳定性和低开关功率（fJ范围）。在第二篇博士论文中，我们计划增加迄今为止非常少的材料数量，允许研究这些效应。特别是具有小电子密度的铁磁和亚铁磁材料是该项目的重点。我们的目标是半导体铁氧体和Mn-Ge系统。对于这两种材料类别，我们已经取得了初步成果。这两种材料类别都是非常有前途的，因为铁氧体是半导体的，并且对于Mn-Ge系统，可以预期垂直各向异性和低金属电子密度。对于这些材料，我们计划首先进行非常薄的外延膜的制备和电场对磁性能的影响的基础研究。后者应通过霍尔效应和反常霍尔效应来研究。这些研究应遵循的实现磁隧道结，允许在膜厚度大于CoFeB系统的电场效应。

项目成果

Correlation of tunnel magnetoresistance with the magnetic properties in perpendicular CoFeB-based junctions with exchange bias

• DOI: 10.1063/1.5062847
• 发表时间: 2019-01-14
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Manos, Orestis;Bougiatioti, Panagiota;Reiss, Guenter
• 通讯作者: Reiss, Guenter

Spin-Transfer Torque Switching at Ultra Low Current Densities

超低电流密度下的自旋转移扭矩切换

• DOI: 10.2320/matertrans.ma201570
• 发表时间: 2015
• 期刊: Materials Transactions
• 影响因子: 1.2
• 作者: Johannes Christian Leutenantsmeyer;Vladyslav Zbarsky;Marvin von der Ehe;Steffen Wittrock;Patrick Peretzki;Henning Schuhmann;Andy Thomas;Karsten Rott;Günter Reiss;Tae Hee Kim;Michael Seibt;Markus Münzenberg
• 通讯作者: Markus Münzenberg

Perpendicular magnetic anisotropy of TiN buffered Co2FeAl/MgO bilayers

• DOI: 10.1063/1.4984891
• 发表时间: 2017-06
• 期刊: Journal of Applied Physics
• 影响因子: 3.2
• 作者: A. Niesen;J. Ludwig;M. Glas;Robin Silber;J. Schmalhorst;E. Arenholz;G. Reiss

Tunneling magnetoresistance of perpendicular CoFeB-based junctions with exchange bias

• DOI: 10.1063/1.4985850
• 发表时间: 2017-09-14
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Manos, Orestis;Boehnke, Alexander;Reiss, Guenter
• 通讯作者: Reiss, Guenter