Bulk contributions to tunnel magnetoresistance in magnetic tunnel junctions

Zhu, Tao; Xiang, X. H.; Shen, Fang; Zhang, Z.; Landry, G.; Dimitrov, Dimitar; Garcı́a, N.; Xiao, John Q.

doi:10.1103/physrevb.66.094423

Cited by 21 publications

(13 citation statements)

References 21 publications

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“…12 The phase shift Φ is sensitive to electric and magnetic fields in the sample and, in the absence of dynamical diffraction and Fresnel contrast effects, is given by the following expression: 13 (1) where C E is an interaction constant, V is the inner potential, and B n is the component of the magnetic field normal to the plane defined by the incident electron-beam paths, i.e., in the y direction. For a specimen of uniform composition and negligible thickness variation, the x gradient of the phase shift is given:…”

Section: Methodsmentioning

confidence: 99%

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Probing tunnel barrier shape and its effects on inversed tunneling magnetoresistance at high bias

Sheng

Wang

Xiang

et al. 2004

Journal of Elec Materi

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We have used an electron holography (EH) technique to directly probe the potential profile of tunnel barriers in magnetic tunnel junctions (MTJs). Barriers with under-, optimum-, or over-oxidized condition have been investigated. One important finding is that there is always slight oxidation of the top electrode because of film morphology. Sharp interfaces can be achieved in the bottom interface of optimally oxidized barrier or both interfaces in MTJs with under-oxidized barriers. We also demonstrate, theoretically and experimentally, how barrier shape affects the bias dependence and, in low barrier height case, result in inversed tunneling magnetoresistance (TMR) at high bias. The mechanism is very different from that responsible for inversed TMR in all biases. The finding leads to the possibilities of achieving better signals at high bias in real applications.

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Section: Methodsmentioning

confidence: 99%

“…1,2 The common Al 2 O 3 barrier is typically formed by oxidizing around the 1.5-nm Al layer, and the barrier quality depends on the film roughness, grain size, and oxidation conditions. The barrier height and barrier thickness are often extracted from current-voltage curves using either Simmons' or Brinkman et al's model.…”

Section: Introductionmentioning

confidence: 99%

Probing tunnel barrier shape and its effects on inversed tunneling magnetoresistance at high bias

Sheng

Wang

Xiang

et al. 2004

Journal of Elec Materi

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“…Fig. 2 shows a HRTEM cross-sectional image of the optimum oxidized MTJ with a nominal Al thickness of about 1.26 nm [3]. The left/right side of the Al O barrier corresponds to the top/bottom electrode, respectively.…”

Section: Structure Analysismentioning

confidence: 99%

“…During plasma oxidation, O pressure was kept at 160 mtorr. And guided by the TMR measurement, the HRTEM samples with over-, optimum, and under-oxidation of Al were cut along the wedge [3]. A Philips CM200 field emission gun TEM equipped with an electrostatic biprism and a Gatan 794 multiscan charge coupled device (CCD) camera was operated at 200 kV to characterize the microstructure.…”

Section: Structure Analysismentioning

confidence: 99%

“…For the former question, so far there is no clear answer for whether the contribution to TMR is from interface or bulk region, although many groups probably lean toward the argument that the tunneling process depends on the wave function of the first atomic layer [1]. However, more recent experiments [2], [3] raise the question about the tunneling characteristic length in MTJs and indicate the bulklike contribution existing in spin polarized tunneling (SPT). For the latter question, a good understanding of the bias dependence of TMR is still lacking.…”

Section: Introductionmentioning

confidence: 96%

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Recent developments in magnetic tunnel junctions

et al. 2003

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The authors present various new phenomena in magnetic tunneling junction (MTJ). Since the interface and barrier structure play a significant role in determining the physical phenomena, they have employed various techniques to characterize this structure. For obtaining the barrier information, they have performed electron holography studies which directly show the energy profile with atomic resolution. The interdiffusion between different layers has been studied using high-resolution transmission electron microscopy, elemental mapping, and time-of-flight secondary ion mass spectrometry. With this structural information, the authors showed the existence of bulklike contribution in MTJ and determined the characteristic length. In addition, they also observed a conductance minimum anomaly which is much different from the normally observed zero bias anomaly. Large inversed TMR has also been observed at bias as high as 0.4 V in MTJs with an Al 2 O 3 -ZrO barrier. The authors have modified the Brinkman model by incorporating the voltage dependent density of states of the ferromagnetic electrodes, which sucessfully explains the bias dependence of the tunneling magnetoresistance (TMR), conductance minimum anomaly, and inversed TMR.Index Terms-Electron holography, magnetic tunneling junction (MTJ), tunneling magnetoresistance (TMR) bias dependence.

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TMR and Al-O Based Magnetic Tunneling Junctions

Han¹

2016

Handbook of Spintronics

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Bulk contributions to tunnel magnetoresistance in magnetic tunnel junctions

Cited by 21 publications

References 21 publications

Probing tunnel barrier shape and its effects on inversed tunneling magnetoresistance at high bias

Probing tunnel barrier shape and its effects on inversed tunneling magnetoresistance at high bias

Recent developments in magnetic tunnel junctions

TMR and Al-O Based Magnetic Tunneling Junctions

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