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首页> 外文会议>International Magnetics Conference >Coexistence of Large Voltage Controlled Magnetic Anisotropy, Large Surface Anisotropy, and Large TMR by a new MTJ structure having MgO/CoFeB/Ir/CoFeB.
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Coexistence of Large Voltage Controlled Magnetic Anisotropy, Large Surface Anisotropy, and Large TMR by a new MTJ structure having MgO/CoFeB/Ir/CoFeB.

机译：具有MgO / CoFeB / IR / CoFeB的新MTJ结构，大压控制磁各向异性，大型表面各向异性和大TMR的共存。

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Summary form only given. In recent years, writing data in magnetic random access memory (MRAM) utilizing voltage controlled magnetic anisotropy (VCMA) has attracted much attention for its potential low power consumption [1]. We proposed voltage -control spintronics memory (VoCSM) which had high -efficient and deterministic writing properties [2]. In order to realize those memories, three features of a large VCMA, a large surface anisotropy Ks, and a large tunneling magnetoresistance (TMR) should coexist. In addition, a large spin -Hall angle is a must for VoCSM. Many challenges based on MgO tunneling barrier/ferromagnetic layer (FL) such as CoFeB thin fi lms combined with various materials as an insertion layer at the MgO/FL interface or as an underlayer of FL showed improved VCMA but were concerned to fail in the coexistence of the feature because of very thin storage -layer or degraded lattice growth between MgO and CoFeB [3], [4], [5]. As a result, none of them have had a practical meaning as a memory cell so far. In this study, the experiments were conducted in which the insertion position of Ir was changed in MgO/CoFeB/Ta thin fi lms. Each of the interface layer, the interlayer and the underlayer of Ir showed an increase in VCMA, and the largest VCMA was obtained in the case of inserting the Ir interlayer into the CoFeB layer. In addition, both the resistance -area product (RA) and TMR ratio decreased greatly when using the Ir interface layer, but clearly improved by employing the Ir interlayer. The base multilayer structure for VCMA measurement was Ta (5 nm)/MgO (~3nm)/CoFeB (1-2 nm)/Ta (5-8 nm), which was deposited on a thermally oxidized Si substrate. The CoFeB layer was set to in -plane magnetization, and the base stack of IrMn/ CoFe/Ru/CoFeB /MgO/CoFeB/Ta with a reference layer was prepared for RA and TMR measurement by using current in -plane tunneling (CIPT). The multilayers for VCMA were patterned and etched into the device size with one side of 3 to 50 μm and their hysteresis curves were measured using the magneto -optical polar Kerr effect. The effective perpendicular magnetic anisotropy fi eld H1c ff of the CoFeB layer was measured while bias voltage was applied to the device, and the variation of Ks depending on the electric field E was evaluated as the VCMA coefficient Figure 1 shows the VCMA coefficients (-dKs/dE) of the MgO/CoFeB/Ta thin films as the "Base" sample, "Interface" sample in which Ir (0.2 or 0.3 nm) is layered at the MgO/ CoFeB interface, "Interlayer" sample in which Ir (0.3 nm) is inserted in the middle of the CoFeB layer, and "Underlayer" sample in which Ir (0.5 nm) is formed between the CoFeB and the Ta layer. All coefficients of the "Interface", "Interlayer", and "Underlayer" samples increased more than that of the "Base" sample in terms of each average value, although each coefficient had a certain degree of dispersion. The Ks in the "Interface" sample also increased more than in the "Base" sample at each average value, however, the largest Ks (maximum of 2.2 erg,/cm 2 ) and VCMA (maximum of 190 fJ/ Vm) were obtained in the "Interlayer" sample. The relationship between RA and TMR ratio in the MTJ samples similar to Fig. 1 with the reference layer is plotted in Fig. 2. Both RA and the TMR ratio in the "Underlayer" sample were almost the same as those in the "Base" sample, but both decreased in the "Interface" sample and further decreased by increasing the Ir layer thickness from 0.2 to 0.3 nm. In the "Interlayer" sample, the deterioration of RA was not observed, and although the TMR ratio decreased, it still showed a high value of more than 120%. By comparison at the Ir thickness of 0.3 nm, it can be seen that both RA and TMR are clearly improved by changing from the Ir interface layer to the Ir interlayer. In summary, we successfully found the practical MTJ structure as a memory cell which realized coexistence of a large VCMA, a large Ks, and a large TMR for the first time. The structure is
机译：摘要表格仅给出。近年来，利用电压控制磁各向异性（VCMA）的磁随机存取存储器（MRAM）中的写入数据引起了其潜在的低功耗[1]的关注。我们提出了具有高效率和确定性写入属性的电压-Control SpintRonics存储器（VOCSM）[2]。为了实现那些存储器，三个具有大VCMA的特征，大表面各向异性Ks和大的隧道磁阻（TMR）应该共存。此外，大型旋转--HALL角度是VOCSM的必须。基于MgO隧道屏障/铁磁层（FL）的许多挑战，例如CoFeB薄膜，与各种材料相结合，作为MgO / FL界面处的插入层或FL的底层显示出改善的Vcma，但涉及在共存中失败由于非常薄的储存 - 层或MgO和CoFeB之间的晶格生长，因此特征[3]，[4]，[5]。因此，其中一定是到目前为止作为存储器单元的实际意义。在该研究中，进行了实验，其中IR的插入位置在MgO / CoFeB / TA薄LMS中改变。界面层中的每一个，IR的中间层和IR底层显示Vcma的增加，并且在将IR层间插入CoFeB层的情况下获得最大的Vcma。此外，当使用IR界面层时，电阻 - 抗性 - 脂肪酰基产品（Ra）和TMR比率均大大降低，但通过使用IR层间清楚地改善。用于VCMA测量的基础多层结构是Ta（5nm）/ mgO（〜3nm）/ cofeb（1-2nm）/ ta（5-8nm），其沉积在热氧化的Si底物上。将CoFeB层设定为在-Plane磁化中，通过在平面隧道（CIPT）中，为RA和TMR测量制备具有参考层的IRMN / COFE / RU / COFEB / MGO / COFEB / TA的基础堆叠。 。 VCMA的多层被图案化并蚀刻到器件尺寸中，使用3至50μm的一侧，并且使用磁光极性克尔效应测量它们的滞后曲线。测量CoFeB层的有效垂直磁各向异性FiELD H1C FF，而偏置电压施加到装置，并且根据VCMA系数图1评估了根据电场E的ks的变化显示VCMA系数（-dks / de）MgO / CoFeB / Ta薄膜作为“基础”样品，“接口”样品，其中Ir（0.2或0.3nm）在MgO / CoFeB界面处层叠，“中间层”样品，其中IR（0.3 nm）插入CoFeB层的中间，并在CoFeB和Ta层之间形成IR（0.5nm）的“底层”样品。 “界面”，“中间层”和“底层”样品的所有系数在每个平均值的方面增加了比“基础”样本的更多，尽管每个系数具有一定程度的分散性。 “界面”样品中的KS也比每个平均值的“基础”样品中的ks增加到，但是，获得最大的Ks（最大2.2 erg，/ cm 2）和vcma（最大为190 fj / Vm）在“中间层”样品中。 MTJ样本中的RA和TMR比的关系类似于图4.在图2中绘制了参考层的图1，“底层”样品中的TM和TMR比例几乎与“基础”中的相同样品，但在“界面”样品中减小，并且通过将IR层厚度从0.2至0.3nm增加，进一步降低。在“中间层”样品中，未观察到Ra的劣化，尽管TMR比率降低，但仍显示出高度超过120％。通过在IR厚度为0.3nm的比较，可以看出，通过从IR接口层改变为IR层间，可以清楚地改善RA和TMR。总之，我们成功地发现了实用的MTJ结构作为第一次实现大VCMA，大KS和大TMR的共存。结构是

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