Study for high speed and high density MRAM development

高速高密度MRAM开发研究

基本信息

批准号：
14076202
负责人：
INOMATA Koichiro
金额：
$ 12.61万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14076202/
关键词：
Spin resonance tunneling effect Double tunneling junctions Epitaxy Conductance oscillation Spin dependent quantum well Heusler alloy Tunnel junction Tunnel magnetoresistance スピン依存量子準位ホイスラー合金薄膜スピン分極率強磁性トンネル効果 L2_1構造 MRAM 磁気抵抗

项目摘要

We have investigated the creation of the spin dependent resonant tunneling devices and the tunnel magnetoresistance of ferromagnetic tunnel junctions (MTJs) using half metallic full-Heusler alloys. Epitaxial double barrier ferromagnetic tunnel junctions (DBTJs) consisting of Fe/MgO/Fe/MgO/Fe were fabricated of a MgO substrate using MBE for the former, in which the intermediate Fe layer thickness was changed. As a result, we have observed the oscillation of the differential conductance as a function of bias voltage for the first time. The oscillation was observed even at RT, although its amplitude was decreased with increasing temperature. The oscillation period increased with decreasing Fe layer thickness. These phenomena are understood by the formation of the quantum well states of Ai band in the middle Fe layer. The TMR is over 100% at RT due to the coherent tunneling and the bias voltage dependence of the TMR is more gentle than that of the single barrier junction and V_<1/2>=1.4 V.For the latter we have studied MTJs using Co_2(Cr_<1-x>Fe_x)Al (CCFA) and concluded that L2_1 structure is difficult to be obtained, which leads to lower spin polarization than that of the calculation. The maximum TMR is 83% at 5K and 54% at RT for x=0.6. We have investigated another Heusler alloy system of Co_2Fe(Al_ySi_<1-y>) and resulted in the observation of the L2_1 structure and integer magnetic moment of 6ujb for Co_2FeSi, suggesting half metallic. The TMR, however, is only 40% at RT for the MTJ using a Co_2FeSi. The maximum TMR at present is 60% at RT for x=0.5 with B2 structure. The further study will lead to higher TMR.

我们已经研究了使用一半金属的全螺旋合金研究的旋转依赖性谐振隧道设备和铁磁隧道连接（MTJ）的隧道磁力。由FE/MGO/FE/MGO/FE组成的外部双屏障铁磁隧道连接（DBTJS）由使用MBE的MGO底物制造，使用MBE为前者制造，其中中间Fe层的厚度更改了中间的Fe层。结果，我们首次观察到差分电导的振荡是偏置电压的函数。即使在RT处观察到振荡，尽管其幅度随温度升高而降低。振荡周期随着FE层厚度的减小而增加。这些现象是通过中间铁层中AI带的量子井状态的形成来理解的。由于连贯的隧穿和TMR的偏差电压依赖性，TMR的RT超过100％，比单个屏障连接的偏置电压依赖性更柔和，V_ <1/2> = 1.4 V.对于后者，我们使用co_2（CR_ <1-x> fe_x> fe_x> fe_x）Al（ccfa）和fert to y2结构l2 to to to portive s and ccfa（ccfa）l2 to to l2 to to l2 with wity l2 with to l2 with wity l2 with to l2 with to l2 with to l2 with to ly2极化比计算的极化。最大TMR为5K时为83％，RT为X = 0.6的最大TMR为54％。我们已经研究了另一种co_2fe（al_ysi_ <1-y>）的Heusler Alloy合金系统，并导致观察到co_2fesi的L2_1结构和6UJB的整数磁矩，这表明半金属。但是，使用CO_2FESI，MTJ的TMR仅在RT时仅为40％。目前，X = 0.5的最大TMR在RT时为60％，具有B2结构。进一步的研究将导致更高的TMR。