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  • 1
    Electronic Resource
    Electronic Resource
    Electrical breakdown of the magnetic tunneling junction with an AlOx barrier formed by radical oxidation (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5194-5196 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, the dielectric breakdown in magnetic tunnel junctions (MTJs) was studied. The MTJ structure is Ta50/NiFe100/Co20/AlOx/Co30/RuRhMn100/Ta50 with the bottom lead of Ta50/Cu500/Ta50 and the top lead of Cu2000/Ta50 (in Å), where the tunneling barrier was formed by 2–20 min radical oxygen oxidation of a 10 Å-thick Al layer. The junctions with area from 2×2 to 20×20 μm2 were patterned using the photolithography process, leading to tunneling magnetoresistance up to 17.2% and resistance-area product ranging from 350 Ω μm2 to 200 kΩ μm2. The junctions studied show dc breakdown voltage from 0.7 to 1.3 V, depending on the junction area and the oxidation time. Long oxidation time up to 14 min and a small junction area results in a large dc breakdown voltage. The electrostatic discharge (ESD) of MTJs was tested by using a human body model. The ESD breakdown voltage increases with decreasing junction resistance. These results are discussed in terms of the E-model based on the field-induced distortion of atomic bonds in the oxide barrier. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373292
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  • 2
    Electronic Resource
    Electronic Resource
    Dependence of tunneling magnetoresistance on ferromagnetic electrode thickness and on the thickness of a Cu layer inserted at the Al2O3/CoFe interface (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5264-5266 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependence of the spin tunneling magnetoresistance (TMR) on the ferromagnetic electrode thickness, tCoFe, and on the thickness of a Cu layer inserted at barrier/ferromagnetic (Al2O3/CoFe) interface is reported. Junctions were fabricated through contact shadow mask or microlithography. Junction TMR increases sharply from zero to a maximum value of 16.4% (shadow masks) with increasing tCoFe from 10 to 30 Å, or to 22% (microlithography) with increasing tCoFe from 6 to 20 Å, and then varies slightly up to tCoFe of 500 Å. The initial increase of TMR with tCoFe up to 30 Å results from the spin-polarization increase in CoFe. This is supported by the magnetization measurement of (Ta 150 Å/CoFe tCoFe)×n multilayers, where the magnetization of CoFe increases from near zero to its bulk value with increase of CoFe thickness from 10 to 40 Å. The incorporation of Cu layers at the Al2O3/CoFe (top electrode) interface decreases the TMR. However, junctions with a 40 Å thick Cu layer added at the Al2O3/CoFe interface still maintain a TMR signal of 1%. The bias voltage dependence of TMR does not vary with the Cu layer thickness added at Al2O3/CoFe interface, implying that it is not significantly dependent on the barrier/ferromagnetic interface. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369849
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic tunnel junctions on magnetic shield smoothed by gas cluster ion beam (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6653-6655 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, a technique, gas cluster ion beam (GCIB), was introduced to smooth the bottom NiFe magnetic shield for magnetic tunnel junction (MTJ) read heads. The GCIB treatment can bring the surface roughness of the shield from 15 to 20 Å to around 5 Å, and the most of scratch marks can be removed. The efficiency of the GCIB process is dependent on the initial surface morphology. The MTJs grown on the magnetic shield smoothed by the GCIB show that the resistance area product RA is increased from 60 to ∼100 Ω μm2 with the GCIB dose up to 1×1016 ions/cm2, arising from a smooth insulating layer, meanwhile, the tunneling magnetoresistance (TMR) is almost constant or slightly decreases. This GCIB process can also improve breakdown voltage (approximately 0.019 V per 1015 ions/cm2) of the MTJs, and slightly increase the ferromagnetic coupling mainly due to the change of the surface morphology. Using this technology, an RA as low as 3.5–6.5 Ω μm2 together with a TMR of 14%–18% can be obtained for MTJs grown on the GCIB treated NiFe magnetic shield. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359217
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature dependence and annealing effects on spin dependent tunnel junctions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5258-5260 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature and annealing effects on junctions with high (10–13 MΩ μm2) and low (25–30 kΩ μm2) resistance-area products were studied. Junction tunneling magnetoresistance (TMR) is almost unchanged and above 20% up to 200 °C. A sharp and reversible TMR decrease is observed between 200 and 220 °C and is due to the exchange loss in the pinning layer. Junction TMR increases from 22% to 26% in high resistance-area product samples (resistance decreases a factor of 2), and from 22% to 37% (resistance increases 30%) in low resistance-area product samples, upon anneal up to 200–230 °C. Rutherford backscattering (RBS) analysis of the oxygen distribution in as-deposited samples indicates oxygen asymmetry in the barrier. This asymmetry and asymmetry in barrier parameters, found in as-deposited samples, disappear after anneal at 200 °C. Two regimes for the TMR dependence on anneal are proposed. The first up to 200 °C, where TMR increases, as barrier is homogenized and polarization near the top electrode increases. The second, above 200 °C in low-resistance junctions, where TMR increase is related with barrier height increase. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369959
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  • 5
    Electronic Resource
    Electronic Resource
    Tunneling magnetoresistance and current distribution effect in spin-dependent tunnel junctions : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6694-6696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, spin-dependent tunnel junctions fabricated by shadow mask (junction area 0.25 mm2) and by lithography (junction area down to 9×2 μm2) were studied. The junctions have NiFe and CoFe electrodes and the insulating barrier Al2O3 is formed by depositing a 10–30 Å thick Al layer, followed by a 1–3 min plasma oxidation in an O2 atmosphere. The mm2-size junctions show tunneling magnetoresistances (TMR) of 10%–13.5% at room temperature (RT), with 50% decrease in TMR for a bias voltage of 220 mV. The junction resistances range from hundreds of Ω to tens of kΩ. The analysis of current distribution indicates that no geometrically enhanced magnetoresistance occurs in the cross-shaped mm2-size junctions when the measured junction resistance is five times larger than the electrode resistance over junction area. The μm2-size junctions show TMR of 17%–24% at RT, independent of the junction area, and have a resistance between 90 kΩ and 1 MΩ for the 9×2 μm2 size (resistance-area products of ∼3 MΩ×μm2). The μm2-size junctions show 50% decrease in TMR for a bias voltage of 430 mV, and high sensitivity (〉20%/Oe). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367719
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  • 6
    Electronic Resource
    Electronic Resource
    Low resistance and high thermal stability of spin-dependent tunnel junctions with synthetic antiferromagnetic CoFe/Ru/CoFe pinned layers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2424-2426 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, submicron-size (down to 0.273 μm2) spin–dependent tunnel junctions with resistance as low as ∼30 Ω μm2 have been fabricated, where the tunneling barrier of AlOx was formed by in situ natural oxidation. These junctions annealed at 250 °C for 5 h showed tunneling magnetoresistance (TMR) of 14.3% and 25.8% for the pinned layers of CoFe/RuRhMn and CoFe/PtMn, respectively, while the TMR is further increased to 31.6% for a synthetic antiferromagnetic pinned layer of CoFe/Ru/CoFe/PtMn due to less interdiffusion at CoFe/Ru interface. The investigation has indicated that the growth of ultrathin Al layer is very sensitive to the surface roughness of bottom ferromagnetic electrode, and large surface roughness leads to small junction resistance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126364
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  • 7
    Electronic Resource
    Electronic Resource
    Large tunneling magnetoresistance enhancement by thermal anneal (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3288-3290 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin tunnel junctions with tunneling magnetoresistance of 36.5%±0.5%, resistance-area product of 35±6 kΩ×μm2, and junction area between 6 and 75 μm2 were fabricated. The barrier height is 2.5±0.3 eV and the barrier thickness is 7.7±0.3 Å. Large tunneling magnetoresistance (TMR) values are obtained by vacuum anneal (at temperatures from 100 to 240 °C for over 5 h) of junctions prepared with as-deposited TMR of 21%±1.7%, and an as-deposited resistance-area product of 25±6 kΩ×μm2. Two regimes occur during anneal. The first one occurs for anneals up to 200 °C where TMR and junction resistance increase, but the barrier parameters are unaltered. The second occurs above 200 °C, where TMR increases faster, together with an increase in barrier height. At 240 °C, TMR starts to decrease. Rutherford backscattering analysis indicates an asymmetry in the oxygen distribution in the as-deposited barrier. The oxygen distribution becomes homogeneous for anneals above 150 °C. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122747
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  • 8
    Electronic Resource
    Electronic Resource
    Low resistance spin-dependent tunnel junctions deposited with a vacuum break and radio frequency plasma oxidized (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 448-450 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin-dependent tunnel junctions with resistance-area products (RJ×A) down to 1.8 kΩ×μm2 and tunneling magnetoresistance (TMR)≥15% were fabricated. Junction areas vary from 6 to 45 μm2. A systematic study of junction resistance and TMR versus deposited Al thickness (tAl=7, 9, 11, and 13 Å), and oxidation time (from 4 to 90 s) is presented. The TMR is maximum (25% to 27%) for tAl=11 Å, with 6 s oxidation time (RJ×A=10 to 20 kΩ×μm2). At 6–10 s oxidation time, reducing the Al thickness from 11 to 7 Å reduces the resistance-area products from 10–20 kΩ×μm2 to 1–3 kΩ×μm2, while TMR decreases from 22%–27% to 13%–17%. Excess oxidation or incomplete oxidation of the Al layer leads to current–voltage curve asymmetry. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123057
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  • 9
    Electronic Resource
    Electronic Resource
    Cell-cell interaction can influence drug-induced differentiation of murine embryonal carcinoma cells
    Amsterdam : Elsevier
    Developmental Biology 109 (1985), S. 25-31 
    Details
    ISSN: 0012-1606
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0012-1606(85)90342-2
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  • 10
    Electronic Resource
    Electronic Resource
    Commitment in a murine embryonal carcinoma cell line during differentiation induced by retinoic acid
    Amsterdam : Elsevier
    Experimental Cell Research 156 (1985), S. 544-552 
    Details
    ISSN: 0014-4827
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0014-4827(85)90561-0
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