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1.
冯玉清  赵昆  朱涛  詹文山 《物理学报》2005,54(11):5372-5376
通过XPS等微观分析手段证实了磁性隧道结在高温退火后,反铁磁层中的Mn元素扩散到被钉 扎铁磁层及势垒层中,破坏了势垒层/铁磁层界面,从而导致了磁性隧道结高温退火后TMR的 下降.然而在反铁磁层和被钉扎铁磁层之间插入一层纳米氧化层后,Mn的扩散得到了抑制, 使磁性隧道结的热稳定性得以提高. 关键词: 磁性隧道结 纳米氧化层 x射线光电子能谱  相似文献   

2.
吴少兵  陈实  李海  杨晓非 《物理学报》2012,61(9):97504-097504
隧道结磁阻(TMR) 传感器及巨磁阻(GMR) 传感器的1/f噪声在低频段噪声功率密度较大, 是影响其低频下分辨率和灵敏度的主要噪声形式. 本文详细介绍了近年来TMR传感器及GMR传感器1/f噪声的特点、来源、理论模型、检测方法及降噪措施等方面的研究进展, 并就隧道结磁阻传感器1/f噪声的物理模型进行了详细解释. 通过纳米模拟软件Virtual NanoLab对不同MgO厚度的Fe/MgO/Fe型磁性隧道结(MTJ) 进行了隧穿概率和TMR变化率的模拟计算, 得到保守估计与乐观估计的TMR变化率, 分别为98.1%与10324.55%, 同时通过MTJ的噪声模型分析了MgO厚度对TMR传感器噪声的影响. 制备了磁屏蔽系数大于10000的磁屏蔽筒并搭建了磁阻传感器1/f噪声的测试平台, 通过测试验证了磁屏蔽系统对环境磁场具有较好的屏蔽效果, 为噪声检测提供了稳定的磁场空间. 最后分析了TMR与GMR中各种因素对传感器噪声的影响, 提出了影响MTJ传感器1/f噪声的因素及一些降噪措施.  相似文献   

3.
在基于磁性隧道结(Magnetic Tunneling Junction,MTJ)的磁随机存储器(Magnetoresistantive Random Access Memory,MRAM)中利用通过MTJ的垂直电流,实现信息写入的新方法,同时给出了基于此新方法的一种新的MRAM结构和驱动原理图,并分析了它的读和写操作的可行性具体过程. 关键词: 垂直电流 磁性隧道结 磁随机存储器  相似文献   

4.
金莲  朱林  李玲  谢征微 《物理学报》2009,58(12):8577-8583
在转移矩阵方法及Mireles和Kirczenow的量子相干输运理论的基础上,研究了正常金属层/磁性半导体层/非磁绝缘层/磁性半导体层/正常金属层型双自旋过滤隧道结中Rashba自旋轨道耦合效应和自旋过滤效应对自旋相关输运的影响.讨论了隧穿磁电阻(TMR)、隧穿电导与各材料层厚度、Rashba自旋轨道耦合强度以及两磁性半导体中磁矩的相对夹角θ之间的关系.研究表明:含磁性半导体层的双自旋过滤隧道结由于磁性半导体层的自旋过滤效应和Rashba自旋轨道耦合作用可获得极大的TMR值.另外TMR和隧穿电导随着Rashba自旋轨道耦合强度的变化而振荡,振荡周期随Rashba自旋轨道耦合强度的增大逐渐减小. 关键词: 双自旋过滤隧道结 Rashba自旋轨道耦合 隧穿磁电阻 隧穿电导  相似文献   

5.
采用磁控溅射,紫外线光刻和离子束刻蚀制备了La2/3Ca1/3MnO3/Eu2CuO4/La2/3Ca1/3MnO3磁性隧道结.通过对获得的磁性隧道结的I-V特性测量,发现非线性的I-V特性,显示结样品的隧穿特性.有趣的是发现在电极材料La2/3Ca1/3MnO3的金属-绝缘体转变温度(Tp)以下,I-V曲线出现一个跳变.随着温度降低,开始出现跳变的临界电流增大,但是跳变都发生在同样的电压下~209mV.当电流增大或减小在跳变点附近出现回滞.这一跳变只发生在铁磁金属态,表明这是一个磁性相关联的效应,可能对应一种新的磁性开关过程.虽然,目前对这一现象背后的物理机理还不清楚,但是,这一现象有可能在未来自旋电子学器件方面具有潜在的应用价值. 关键词: 庞磁电阻 磁性隧道结 开关效应  相似文献   

6.
利用同步辐射光电子能谱(SRPES)和X射线光电子能谱(XPS)技术,系统研究了室温下Fe/ZnO界面形成过程中Fe薄膜与氧结尾的ZnO(000 1 )衬底之间的相互作用,结果显示初始沉积的Fe明显被表面氧氧化为Fe2+离子,在Fe覆盖度为0—3 nm的范围内,分别观察到与界面电荷传输、化学反应以及薄膜磁性相关的三个有意义的临界厚度,这一结果将有助于基于Fe/ZnO界面的相关器件的设计和研发. 关键词: Fe/ZnO 界面作用 同步辐射光电子能谱 X射线光电子能谱  相似文献   

7.
王立锦  滕蛟  于广华 《物理学报》2006,55(8):4282-4286
通过分子束外延(MBE)和脉冲激光沉积(PLD)方法,将1—10个Fe原子层(ML)以楔形方式沉积到反铁磁单晶NiO(001)基片上.表面磁光克尔效应的原位测试结果表明:通过MBE沉积的Fe原子层在Fe/NiO界面处产生了约2ML的磁死层;而通过PLD沉积的Fe原子层在Fe/NiO界面处产生了约3ML的磁死层.X射线光电子能谱对Fe/NiO界面进行研究的结果表明,在Fe原子与单晶NiO间发生了界面化学反应. 关键词: 磁性薄膜 表面磁性 X射线光电子能谱  相似文献   

8.
重点研究了磁性隧道结(MTJ)的电学性能受离子注量影响的物理规律。实验首次发现了高能Ta离子辐射损伤导致MTJ电学功能失效的现象,主要失效模式为:高、低电阻态失效,其中79.9%的功能失效为高电阻态失效。计算表明,单个10.9 MeV/u的Ta离子辐照引入的损伤无法导致MTJ宏观电学功能失效。结合理论计算与Monte Carlo模拟分析,MTJ中的绝缘势垒层与铁磁薄膜的损伤是出现高、低电阻态失效的内因。  相似文献   

9.
研究发现在磁隧道结的反铁磁层和被钉扎铁磁层之间插入一层纳米氧化层,可以使磁隧道结的退火温度增加了40℃,即明显地提高了磁隧道结的温度稳定性.通过卢瑟福背散射实验直接观察到产生这一效应的原因是该纳米氧化层有效地抑制了Mn元素在退火过程中的扩散,从而使TMR值在较高的退火温度下得以保持. 关键词: 磁性隧道结 隧穿磁电阻 热稳定性 纳米氧化层  相似文献   

10.
利用磁控溅射方法沉积双势垒磁性隧道结多层膜, 其中Al-O势垒层由等离子体氧化1 nm厚的 金属铝膜方式制备,然后采用深紫外光曝光和Ar离子刻蚀技术、微加工制备出长短轴分别为 6和3 μm大小的椭圆形双势垒磁性隧道结(DBMTJ),并在室温和低温下对其自旋电子输运 特性进行了研究. DBMTJ的隧穿磁电阻(TMR)比值在室温和42 K分别达到27%和423%, 结电阻分别为136 kΩ·μm2和175 kΩ·μm2,并在实验中观 察到平行状 态下存在低电阻态及共振隧穿效应,反平行态下呈现高电阻态以及TMR随外加偏压或直流电 流的增加而发生振荡现象. 由此,设计了一种基于这种双势垒磁性隧道结隧穿特性的自旋晶 体管. 关键词: 双势垒磁性隧道结 隧穿磁电阻 共振隧穿效应 自旋晶体管  相似文献   

11.
Amorphous rapidly quenched ribbons of (Fe–Co)79Mo8Cu1B12 and (Fe–Co)76Mo8Cu1B15 with the ratio of Co/Fe from 0 to 1 and 0 to 2, respectively, were prepared by planar flow casting. The dependence of Curie temperature TC on Co/Fe ratio was determined from temperature dependencies of sample dilatation measured using a special dilatometer designed for these materials. Due to the presence of the invar effect, it was possible to measure the spontaneous volume magnetostriction in the temperature interval between 300 K and TC, which is of the order of 10−3. Using special disc-shaped samples field dependencies of magnetostriction in parallel and perpendicular directions of the applied magnetic field were obtained by direct measurement. Subsequently, saturation magnetostriction and volume magnetostriction as well as forced magnetostriction were computed. Saturation magnetostriction λS increases with increasing Co/Fe ratio from 0 up to 15 and from 0 up to 17 ppm for both alloy systems, respectively, depending both on the Co/Fe ratio and on the shift of TC with composition. After attaining the maximal value and further increase of the Co/Fe ratio the saturation magnetostriction decreases. Both alloy systems with ratio Co/Fe=0 exhibit TC near room temperature and the system passes into paramagnetic state. TC for higher Co/Fe ratios approaches the glass transition region. In paramagnetic state the field dependencies of magnetostriction are practically linear functions of applied field and approach saturation only for high-field values.  相似文献   

12.
The undoped, Fe-doped, N-doped and Fe+N codoped titanium dioxide (TiO2) samples were synthesized. Detailed analysis shows that all the samples are pure anatase with the shape of a nanorod, and N and Fe ions are incorporated into the TiO2 lattice. For all the samples, the saturation magnetization at room temperature is in the order of the Fe+N codoped TiO2>N-doped TiO2>Fe-doped TiO2>undoped TiO2. Upon N doping, enhanced ferromagnetic properties were observed. The N content in Fe+N codoped TiO2 is about two times as large as that in the N-doped TiO2, which may account for the largest saturation magnetization observed in Fe+N codoped TiO2. It is suggested that metal ion and N codoping may provide a new approach for increasing the saturation magnetization in TiO2-based dilute magnetic semiconductors.  相似文献   

13.
In this work, the magnetic and transport properties of Fe/SiO2/Ni and Fe/SiO2/Co multilayers grown on Si/SiO2 substrates have been studied. The samples have been prepared by two-stage deposition process. In the first stage, Fe layer and SiO2 interlayer of both samples are grown by ion beam deposition technique at room temperature. Then the samples are taken out to ambient atmosphere and loaded into a pulse laser deposition (PLD) chamber. Prior to the deposition of top layer, the samples are cleaned by annealing at 150 °C. In the second stage, Ni (or Co) layer is prepared by PLD technique at room temperature. The thickness of deposited layers has been measured by Rutherford back scattering (RBS). Magnetic properties of ferromagnetic bilayers have been investigated by room-temperature ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM) techniques. Standard four-point magneto-transport measurements at various temperatures have been performed. Two-step switching in the in-plane hysteresis loops of Fe/SiO2/Ni and Fe/SiO2/Co samples is observed. A crossing in the middle of hysteresis loops of both samples points to a weak antiferromagnetic interaction between the magnetic layers of the stacks. Saturation magnetization values have been obtained from the VSM measurements of samples with DC magnetic field perpendicular to the films surface. Magneto-transport measurements have shown the predominant contribution of anisotropic magnetic resistance both at room and low temperatures. FMR studies of Fe/SiO2/Ni and Fe/SiO2/Co samples have revealed additional non-uniform (surface and bulk SWR) modes, which behavior has been explained in the framework of the surface inhomogeneity model. An origin of the antiferromagnetic interaction has been discussed.  相似文献   

14.
In this paper, lead hexaferrite (PbFe12O19) nanoparticles were synthesized by sol-gel method. In order to prepare PbFe12O19 nanoparticles, the metal nitrates with Fe/Pb?=?8, 10, 11, 12, 14 ratios and citric acid were used. The structure, morphology, magnetic, and dielectric properties of PbFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), vibrating sample magnetometer (VSM) and LCR meter. XRD results revealed that the samples with Fe/Pb?≤?10 and Fe/Pb?>?10 have single-phase hexaferrite and hematite (α- Fe2O3) structures, respectively. As a result, the sample with Fe/Pb?=?10 is single-phase and shows the highest values of the saturation magnetization and remanence magnetization. We found that the values of dielectric constant (ε′) and dielectric loss (ε″) increase with an increase in the Fe/Pb molar ratio from 8 to 12 and then decreases with an increase of Fe/Pb molar ratio to 14. The variation of ac conductivity (σac) with frequency ranging from 1?kHz to 200?kHz showed that electrical conductivity in these ferrites is mainly due to the electron hopping mechanism.  相似文献   

15.
Metastable alloys of Ag1-xFex (x=0.17, 0.30, 0.50, 0.54, 0.56 and 1.0) and the stable Au1-yFey (y=0.18 and 0.25) alloy were prepared as thin films by vapor quenching method on low temperature kapton substrate. The X-ray diffraction spectra of all Ag/Fe samples. withx<-0.56, have indication of fee structure with very small grain size. The present work reports in-situ Mössbauer results on Ag/Fe and Au/Fe films. The spectra obtained are characteristic of homogeneous disordered alloy with broad magnetic hyperfine field distribution. Aging effect inducing cluster formation was observed in Ag/Fe films after they were heated to room temperature, but this behavior was not detected in Au/Fe samples.  相似文献   

16.
Magnetization and magneto-resistance experiments have been carried out on well characterized samples of the GdBaCo2−xFexO5.5 series. Zero field cooled magnetization measurements in the low concentration Fe samples suggest, that the low temperature anti-ferromagnetic phase transforms sequentially to several ferromagnetic phases, before transforming to a paramagnetic state with increase in temperature. The anti-ferromagnetic to the first ferromagnetic phase transition is associated with a large negative magneto-resistance for Fe fractions upto x=0.075. Isothermal magnetization measurements in the ferromagnetic like region of the samples, suggests the presence of mixtures of two ferromagnetic phases. Similar measurements performed at low temperatures where anti-ferromagnetic-like phase is stabilised suggest the presence of a mixture of anti-ferromagnetic and ferromagnetic phases. Magnetization and magneto-resistance are seen to collapse for Fe fractions, x>0.1. Based on these studies a plausible scenario of the evolution of magnetism with Fe substitution in GdBaCo2O5.5, is suggested.  相似文献   

17.
研究了高频溅射制备的Fe/SnO2非晶多层膜的磁特性.当SnO2层厚度ds固定为5nm时,样品的饱和磁化强度Ms随Fe层厚度dm的减小而降低,这主要受样品的死层效应和维度效应的影响.另外,在dm很小时,样品呈现准二维磁性.样品居里温度TC随dm的减小单调下降.样品矫顽力Hc随dm的变化呈现 关键词:  相似文献   

18.
We present x-ray diffraction experiments and multiple-scattering calculations on the structure and transport properties of a Fe/MgO/Fe(001) magnetic tunnel junction (MTJ). Coherent growth of the top Fe electrode on the MgO spacer is observed only for Fe deposition in ambient oxygen atmosphere leading to a coherent and symmetric MTJ structure characterized by FeO layers at both interfaces. This goes in parallel with calculations indicating large positive tunnel magnetoresistance (TMR) values in such symmetric junctions. The results have important implications for achieving giant TMR values.  相似文献   

19.
鲁毅  李庆安  邸乃力  成昭华 《物理学报》2003,52(6):1520-1523
对Nd0.5Sr0.4Pb0.1Mn1-xFex O3系列多晶样品的结构,磁和转变特性进行了实验研究.在x=0.00—0.10的范围内获得了单相样品,Fe3+的替代并没有引起整个系列的结构变化,然而Mn位的掺杂却强烈地抑制了Nd 0.5Sr0.4Pb0.1MnO3的铁 关键词: 磁结构 磁性 P')" href="#">磁转变温度TP 双交换作用  相似文献   

20.
研究了溶胶-凝胶法制备氧化物巨磁电阻材料的工艺,制备了La0.7Sr0.3< /sub>CrxMn1-xO3(x=0,0.10,0.15)和La0.7Sr0.3FexMn1-xO3(x=0.05,0.10,0.16)两 系列的单相钙钛矿锰氧化物多晶样品,并研究了Cr,Fe替代La0.7Sr0.3MnO3中部分Mn后对其结构、磁性和巨磁电阻性质的影响.观察到La0.7 Sr0.3Cr0.15Mn0.85O3和La0. 7Sr0.3Fe0.05Mn0.95O3两个样品的 电阻-温度曲线都出现了双峰.定性讨论了可能产生双峰的机制.随Cr(或Fe)替代量的增加, 材料的居里温度很快下降,铁磁性减弱,导电性降低,巨磁电阻效应增强.但与Fe掺杂相比 ,相同数量的Cr掺杂对材料的影响要小. 关键词: 巨磁电阻效应 溶胶-凝胶工艺 电阻-温度曲线 金属绝缘体转变  相似文献   

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