Effect of bias voltage and interdiffusion in Ir-Mn exchange-biased double tunnel junctions

Saito, Y.; Amano, M.; Nakajima, Kazuyoshi; Takahashi, Shigeki; Sagoi, Masayuki; Inomata, K.

doi:10.1109/20.951027

Cited by 20 publications

(20 citation statements)

References 14 publications

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“…20 Accordingly, magnetic atoms will also diffuse into barrier layers if the annealing temperature is high. 21 For our case, due to the AlO x layers and ferromagnetic layers interdiffused in the asdeposited condition, the AlO x layers were relatively enlarged and the middle ferromagnetic layers were shrunk, respectively. Thus, a low TMR is inevitable.…”

Section: Resultsmentioning

confidence: 95%

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Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

Wang

Zeng

Sharif

et al. 2006

Journal of Applied Physics

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Barrier shapes and its detailed microstructures in the double barrier magnetic tunnel junctions were intensively investigated by both high resolution transmission electron microscopy and electron holography. Two broad (>2nm) potential wells (i.e., shapes of AlOx layers) with slanted interfaces were observed in the electron hologram of the as-deposited samples. However, in the hologram of the annealed samples, two narrowed (down to 1.18nm) and almost equal (height) potential wells with sharp and steep interfaces were acquired. This indicates that the value of tunnel magnetoresistance can be increased from 12.8% to 29.4% at room temperature by annealing treatment where the sharpness and height of the barriers played a critical role.

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Section: Resultsmentioning

confidence: 95%

“…20,21 Postannealing can make elements, such as oxygen, redistribute uniformly within the AlO x barrier layer. 20 Accordingly, magnetic atoms will also diffuse into barrier layers if the annealing temperature is high.…”

Section: Resultsmentioning

confidence: 99%

Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

Wang

Zeng

Sharif

et al. 2006

Journal of Applied Physics

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“…A possible solution is to use double-barrier magnetic tunnel junctions ͑DMTJs͒ where the applied voltage is divided over two single junctions. Experimental studies on DMTJs with amorphous Al 2 O 3 barriers [14][15][16] and fully epitaxial Fe/ MgO double-barrier structures 17 have indeed confirmed a slower decay of the TMR ratio with bias voltage. In this letter, we demonstrate that high quality double-barrier junctions with crystalline MgO barriers and CoFeB electrodes can be fabricated by magnetron sputtering and postdeposition annealing.…”

mentioning

confidence: 91%

Influence of annealing on the bias voltage dependence of tunneling magnetoresistance in MgO double-barrier magnetic tunnel junctions with CoFeB electrodes

Feng

Dijken

Coey

2006

Applied Physics Letters

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Double-barrier magnetic tunnel junctions with two MgO barriers and three CoFeB layers exhibiting tunneling magnetoresistance ͑TMR͒ values of more than 100% were fabricated. The bias voltage dependence of the TMR ratio is highly asymmetric after annealing at low temperatures, indicating dissimilar CoFeB / MgO interfaces. The TMR effect decays very slowly for positive bias and is only reduced to half of its maximum value at V 1/2 = 1.88 V when the junctions are processed at 200°C. The largest output voltage, 0.62 V, is obtained after annealing at 300°C, a temperature that combines high TMR ratios with a considerable asymmetric bias dependence. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2362977͔Following the demonstration of large tunneling magnetoresistance ͑TMR͒ ratios and low resistance-area products in magnetic tunnel junctions with a crystalline MgO͑001͒ barrier, MgO is now considered as the key barrier material for next-generation device applications. Giant TMR ratios well above 100% at room temperature have been obtained with epitaxial Fe/ MgO / Fe junctions, 1-5 textured magnetic tunnel junctions ͑MTJs͒, 6 and CoFeB / MgO / CoFeB structures. [7][8][9][10][11] In the latter case, the MgO barrier grows with a highly oriented ͑001͒ texture on top of an amorphous CoFeB layer. A postdeposition annealing process then crystallizes the CoFeB electrodes, thereby creating the different Bloch state symmetries with dissimilar decay rates in the MgO barrier that are necessary for giant TMR values. 12,13 In practical applications, MTJ structures are biased to increase the output voltage and decrease its signal-to-noise ratio. Electronic structure effects, magnon excitations, and spin-flip scattering on interface defects, however, reduce the TMR effect at elevated bias voltage and this limits the output signal of MTJ sensors and memory elements. A possible solution is to use double-barrier magnetic tunnel junctions ͑DMTJs͒ where the applied voltage is divided over two single junctions. Experimental studies on DMTJs with amorphous Al 2 O 3 barriers [14][15][16] and fully epitaxial Fe/ MgO double-barrier structures 17 have indeed confirmed a slower decay of the TMR ratio with bias voltage. In this letter, we demonstrate that high quality double-barrier junctions with crystalline MgO barriers and CoFeB electrodes can be fabricated by magnetron sputtering and postdeposition annealing. The bias voltage dependence of the TMR is asymmetric and depends strongly on the annealing temperature. These results can be used to engineer MTJs with high output signals.The DMTJs consisting of a 5 Ta/50 Ru/5 Ta/5 NiFe/10 IrMn/2 CoFe/0.7 Ru/4 CoFeB/2.5 MgO/3 CoFeB/2.5 MgO/4 CoFeB/0.7 Ru/2 CoFe/10 IrMn/5 NiFe/5 Ta ͑thickness in nanometers͒ multilayer stack were grown by magnetron sputtering on thermally oxidized Si substrates in our Shamrock deposition tool. All metallic layers were deposited by dc sputtering and a Co 40 Fe 40 B 20 ͑at. %͒ alloy target was used for the ferromagnetic electrodes. The MgO barriers were fabricated by rf ...

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“…This value decreases to 330 mV at 50 K. V 1/2 in the pMTJ devices is smaller than that of in-plane anisotropy MTJs with AlO x barriers, where it usually exceeds 600 mV at room temperature. 18 This may indicate that AlO x barrier quality is poorer in the pMTJ stacks. In order to achieve strong perpendicular magnetic anisotropy, we used 10 nm Pt as a seed layer to induce good (111) texture for Co/Pt multilayers, but this may increase the roughness of the whole stack, especially at the bottom interface between the Co/Pt electrode and the AlO x barrier.…”

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confidence: 99%

Temperature dependent coercivity crossover in pseudo-spin-valve magnetic tunnel junctions with perpendicular anisotropy

Feng¹,

Wu²,

Feng³

et al. 2011

Applied Physics Letters

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We report the temperature dependent collapse of tunnel magnetoresistance (TMR) in perpendicular anisotropy magnetic tunnel junctions (pMTJs) with AlO x barriers and (Co/Pt) 3 multilayer electrodes, due to the coercivity crossover of the top and bottom (Co/Pt) 3 stacks. The different temperature dependence of two (Co/Pt) 3 stacks in pMTJs is mainly caused by the additional perpendicular anisotropy created at interface between the ferromagnetic electrode and the AlO x barrier.

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Effect of bias voltage and interdiffusion in Ir-Mn exchange-biased double tunnel junctions

Cited by 20 publications

References 14 publications

Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

Influence of annealing on the bias voltage dependence of tunneling magnetoresistance in MgO double-barrier magnetic tunnel junctions with CoFeB electrodes

Temperature dependent coercivity crossover in pseudo-spin-valve magnetic tunnel junctions with perpendicular anisotropy

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