Real-time evolution of tunneling magnetoresistance during annealing in CoFeB∕MgO∕CoFeB magnetic tunnel junctions

Wang, W. G.; Ni, Chaoying; Rumaiz, Abdul K.; Wang, Y.; Fan, Xin; Moriyama, Takahiro; Cao, Rong; Wen, Qiye; Zhang, H. W.; Xiao, John Q.

doi:10.1063/1.2903147

Cited by 38 publications

(25 citation statements)

References 28 publications

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“…A rapid increase of the TMR ratio is seen at the beginning, in particular for annealing temperatures of 300 • C and above, followed by a slower increase. The same behavior has been reported by Wang et al before [17]. In a subsequent paper [18], these authors studied the kinetics of crystallization processes by x-ray diffraction and electron microscopy and identified the crystallization of CoFeB in an inhomogeneous solid-state epitaxy mode.…”

Section: Resultssupporting

confidence: 58%

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Conductance anomalies of CoFeB/MgO/CoFeB magnetic tunnel junctions

et al. 2014

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The I -V characteristics of CoFeB/MgO/CoFeB magnetic tunnel junctions show pronounced nonlinearities which are relevant both for sensor applications and for the basic understanding of spin-dependent tunneling. To study the relation between the tunnel characteristics and the tunnel magnetoresistance (TMR) ratio, a series of CoFeB/MgO/CoFeB junctions was annealed with stepwise increasing annealing time at different temperatures. The related TMR ratio and the I -V characteristics were measured in the temperature range between 15 K and 300 K. This allowed the comparison of I -V characteristics of the same junction for TMR ratios between 25% and 150% at 300 K thus eliminating the influence of variations in the preparation process of separate individual samples. In addition to a zero bias anomaly observed in particular at low temperatures and for large TMR ratios, a conductance anomaly in the I -V curves was observed around a bias voltage of 350 mV. A general correlation between the deviation from Ohmic I -V characteristics and the TMR ratio was found both for parallel and antiparallel magnetizations of both ferromagnetic layers. This means that the shape of the I -V curves directly scales with the spin polarization of the tunneling current and the proportion of coherent electron tunneling. Both the 350 mV conductance anomaly and the correlation between non-Ohmic characteristics and the TMR ratio can be explained by considering the contributions of the relevant majority and minority spin bands of the ferromagnetic contacts.

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Section: Resultssupporting

confidence: 58%

“…The kinetics of the processes occurring during annealing have been studied in detail [17][18][19]. Specific useful information has been obtained from the time evolution of the TMR ratio during annealing.…”

Section: Introductionmentioning

confidence: 99%

Conductance anomalies of CoFeB/MgO/CoFeB magnetic tunnel junctions

et al. 2014

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“…14 High TMR ratio over 400% was observed for MTJs with x = 20% and 40%. It has been suggested that the high TMR ratios at T a above 475°C are related to the improved quality of MgO barrier, 17,18 in addition to the crystallization of initially amorphous CoFeB to highly oriented bcc ͑001͒ textured CoFeB. 4,19,20 Note that CoFeB electrodes start to form bcc ͑001͒ textures at a much lower annealing temperature of T a = 325°C ͑Refs.…”

mentioning

confidence: 97%

Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature

Ikeda¹,

Hayakawa

Ashizawa³

et al. 2008

Applied Physics Letters

1,354

728

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Assembled Fe3O4 nanoparticles on graphene for enhanced electromagnetic wave losses Appl. Phys. Lett. 101, 153108 (2012) Magnetization reversal and magnetoresistance behavior of perpendicularly magnetized [Co/Pd]4/Au/[Co/Pd]2 nanowires J. Appl. Phys. 112, 073902 (2012) Electric-field control of CoFeB/IrMn exchange bias system J. Appl. Phys. 112, 064120 (2012) Critical effect of spin-dependent transport in a tunnel barrier on enhanced Hanle-type signals observed in threeterminal geometry Appl. Phys. Lett. 101, 132411 (2012) Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by halfmetallicity of Co2MnSi and coherent tunneling

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“…This work confirms a crystalline albeit textured and columnar growth after annealing of both MgO and CoFe, layers. Wang et al 11 confirmed by x-ray scattering an improved crystallinity of the MgO͑001͒ layer as the reason for the increasing TMR value measured at high annealing temperatures. At 380°C, the MgO͑002͒ Bragg reflection intensity increases with annealing time and the full width at half maximum ͑FWHM͒ decreases.…”

Section: Introductionmentioning

confidence: 70%

The effect of annealing on the junction profile of CoFeB/MgO tunnel junctions

Zhernenkov

Vadalá

et al. 2010

Journal of Applied Physics

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The tunnelling magnetoresistance of CoFeB/MgO tunnel junctions is exceptionally high, although the electrodes and the barrier are grown at room temperature in the amorphous state. For their functionality annealing steps up to high temperatures are required. We have analyzed in detail the changes in the chemical and magnetization profile upon annealing up to 360°. The multilayers used for this study are similar to those which are used in magnetic tunnel junctions, however with five repeats. In particular, we have used hard non-resonant and soft resonant magnetic x-ray scattering in order to unravel any changes upon annealing. The multilayers exhibit superior structural quality, which hardly changes with annealing. Surprisingly, only little recrystallization of the CoFeB and the MgO layers can be discerned by x-ray diffraction.

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Real-time evolution of tunneling magnetoresistance during annealing in CoFeB∕MgO∕CoFeB magnetic tunnel junctions

Abstract: Articles you may be interested inEffects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions

Cited by 38 publications

References 28 publications

Conductance anomalies of CoFeB/MgO/CoFeB magnetic tunnel junctions

Conductance anomalies of CoFeB/MgO/CoFeB magnetic tunnel junctions

Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature

The effect of annealing on the junction profile of CoFeB/MgO tunnel junctions

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