High inverted tunneling magnetoresistance in MgO-based magnetic tunnel junctions

Feng, J. F.; Feng, G.; Coey, J. M. D.; Han, X. F.; Wang, Zhan

doi:10.1063/1.2779241

Cited by 12 publications

(27 citation statements)

References 23 publications

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“…͑001͒-oriented MgO barrier can be achieved and a high TMR ratio of 155% was observed in MTJs with a thick pinned CoFeB layer. 15,16 The resistance-area products are of order 10 6 ⍀ m 2 and a nonlinear current-voltage characteristic is observed for MgObased MTJs with a thin CoFeB layer. 15 After depositing the MTJ stack, microscale MTJs were fabricated using conventional UV lithography.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…15,16 The resistance-area products are of order 10 6 ⍀ m 2 and a nonlinear current-voltage characteristic is observed for MgObased MTJs with a thin CoFeB layer. 15 After depositing the MTJ stack, microscale MTJs were fabricated using conventional UV lithography. High vacuum thermal annealing of the patterned junctions with an area from 12ϫ 12 to 24ϫ 24 m 2 was carried out for 1 h in an applied magnetic field of 800 mT.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…15 The 20 ͑3͒ / Ta͑5͒ / Ru͑5͒ ͑thickness in nanometers͒ and the order is from the bottom electrode to the top. All multilayers were grown under high vacuum ͑10 −7 Torr͒ and at room temperature in a Shamrock sputtering tool.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…15 The inverted TMR was due to the imbalance of the SAF stack. Here we examine the temperature dependence of the junction resistance and the inverted TMR effect for these MgO-based MTJs, which is related to the superparamagnetism.…”

Section: Introductionmentioning

confidence: 99%

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Superparamagnetism in MgO-based magnetic tunnel junctions with a thin pinned ferromagnetic electrode

et al. 2010

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MgO-based magnetic tunnel junctions have been fabricated with a thin Co 40 Fe 40 B 20 ͑CoFeB͒ layer in the pinned synthetic antiferromagnetic CoFe/Ru/CoFeB stack. An inverted tunneling magnetoresistance is observed due to the unbalanced synthetic antiferromagnet. Superparamagnetic nanoparticles form when the CoFeB layer is thinner than 1.5 nm, and an abnormal temperature dependence of the junction resistance is associated with superparamagnetism when the thermal fluctuation energy exceeds the magnetic anisotropy energy. This explanation accounts for the temperature dependence of the tunneling magnetoresistance effect.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Superparamagnetism in MgO-based magnetic tunnel junctions with a thin pinned ferromagnetic electrode

et al. 2010

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“…Further details on the sample growth process and measurement can be found in Refs. [20][21][22]. Figure 1 shows MR curves for an EB-MTJ and a rf-MTJ.…”

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confidence: 99%

Reduced low frequency noise in electron beam evaporated MgO magnetic tunnel junctions

Diao

Feng

et al. 2010

Applied Physics Letters

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We compare low frequency noise in magnetic tunnel junctions with MgO barriers prepared by electron-beam evaporation with those prepared by radiofrequency sputtering, both showing a high tunneling magnetoresistance. The normalized noise parameter in the parallel state of junctions with evaporated barriers is at least one order of magnitude lower than that in junctions with sputtered barriers, and exhibits a weaker bias dependence. The lowest normalized noise is in the 10 −11 m 2 range. A lower density of oxygen vacancies acting as charge trap states in the evaporated MgO is responsible for the lower noise. © 2010 American Institute of Physics. ͓doi:10.1063/1.3431620͔Magnetic tunnel junctions ͑MTJs͒ have attracted a great deal of attention since the demonstration of the tunneling magnetoresistance ͑TMR͒ effect at room temperature. 1,2 Following theoretical predictions, 3,4 a large TMR ratio of up to 200% at room temperature in MTJs with CoFeB electrodes and MgO tunnel barriers was achieved. 5,6 A record room temperature TMR of 604% has since been reported in a pseudospin valve stack, 7 which is close to the theoretical maximum. 3,4 Major advances in MTJs have led to important applications in hard-disk read heads, 8 sensors, 9 and magnetic random access memory. 10 For magnetic field sensing applications, both signal and noise in the MTJ are of equal significance. It has been found previously that 1 / f noise usually dominates other kinds of noise, e.g., thermal noise and shot noise, at frequencies up to a few kilohertz in an MTJ device, and it limits the low-frequency sensitivity. [11][12][13][14][15][16] The 1 / f noise in these devices is normally quantified by the Hooge parameter ␣, defined as AfS V / V 2 , in which A is the junction area, f the frequency, S V the noise power spectrum density, and V the voltage applied to the MTJ. 12,17 In conventional radio frequency ͑rf͒ sputtered MTJs with CoFeB electrodes and MgO tunnel barriers, ␣ was reported to decrease as a function of annealing time and reach a minimum value of 2 ϫ 10 −10 m 2 . 18 The lowest ␣ value ever observed in MTJs, between ͑1-5͒ ϫ 10 −11 m 2 , was achieved in fully epitaxial Fe͑100͒/MgO͑100͒/Fe͑100͒ junctions grown by molecular beam epitaxy ͑MBE͒. 19 Recently, some of us suggested electron-beam evaporation as an alternative to MBE or rf-sputtering for growing high quality MgO tunnel barriers. The junctions fabricated in this way have been shown to possess high TMR ratios of ϳ240% at room temperature and a reduced density of oxygen vacancies, compared to counterparts grown entirely by rf-sputtering. 20 In this work, we report on low frequency noise in the MTJs with electron-beam evaporated MgO barriers of different thicknesses ͑EB-MTJs͒, comparing it to that measured in our MTJs with rf-sputtered MgO tunnel barriers ͑rf-MTJs͒. We show that the Hooge parameter ␣ in the EB-MTJs in their parallel state is at least one order of magnitude lower than that in the rf-MTJs, across a large range of resistance-area ͑RA͒ product 5 ϫ 10 2 Ͻ RAϽ 1 ϫ 10 6 ⍀ m 2 ...

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Change Character of Conductivity in Metal–Insulator–Metal Thin Films

Burlakov

Filatov

Pogorelov

2021

Physica Status Solidi (b)

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Herein, the possibility of changing the conductivity of thin‐film systems consisting of two metals separated by an insulator (metal–insulator–metal, MIM) is shown. The electrophysical properties are studied in three systems: Fe/MgO/Ni, Fe/MgO/Co, and Fe/MgO/Fe + C (Fe doped with carbon). The resulting inhomogeneity in thickness of the dielectric layer over the junction area promotes the appearance of local conduction regions. This makes it possible to change the type of conductivity from tunneling to semiconducting. As a result, a region with negative differential resistance is observed in I–V characteristics of MIM systems. The processes of electromigration during the alloying of one of the metal layers are considered. Presence of such processes is confirmed by the results of dynamic and static measurements of conductivity and corresponding assessments. Exposure of the sample in laboratory atmosphere at room temperature for several tens of days provides asymmetrical I–V characteristics. This indicates the rectifying properties of the contact—characteristic of the conductivity of the Schottky diode. The use of MIM systems with the described properties is considered promising for application in modern electronic devices as basic elements and memory cells.

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High inverted tunneling magnetoresistance in MgO-based magnetic tunnel junctions

Cited by 12 publications

References 23 publications

Superparamagnetism in MgO-based magnetic tunnel junctions with a thin pinned ferromagnetic electrode

Superparamagnetism in MgO-based magnetic tunnel junctions with a thin pinned ferromagnetic electrode

Reduced low frequency noise in electron beam evaporated MgO magnetic tunnel junctions

Change Character of Conductivity in Metal–Insulator–Metal Thin Films

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