MTJ Elements With MgO Barrier Using RE-TM Amorphous Layers for Perpendicular MRAM

Hatori, T.; Ohmori, Hideto; Tada, Masaru; Nakagawa, Shigeki

doi:10.1109/tmag.2007.894013

Cited by 21 publications

(4 citation statements)

References 7 publications

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“…In recent years, a great deal of attention has been paid to the material-engineering of ultrathin magnetic multilayer system having perpendicular magnetic anisotropy (PMA); with consideration to their prominence for advanced spin-transfer-torque fabrication challenges such as the requirement of high temperature for FePt [29][30][31][32][33][34]. On the other hand, multilayers such as Co/Pd, Co/Pt and Co/Ni multilayers provide an opportunity to tune the properties in a controllable manner.…”

Section: Introductionmentioning

confidence: 99%

[Co/Ni] multilayers with robust post-annealing performance for spintronics device applications

Gupta¹,

Sbiaa²,

Bahri³

et al. 2018

J. Phys. D: Appl. Phys.

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The effect of annealing on the diffusion induced changes in the magnetic and magnetodynamic properties of (Co/Ni) multilayers were investigated. Here, we report, all aspects of post annealing induced effect on perpendicular magnetic anisotropy (PMA), domain morphology, switching mechanism and high frequency magnetization dynamics to understand spin relaxation. (Co/Ni) multilayers of this study exhibited a loop squareness of 95%, a slight drop in saturation magnetization from 650 emu/cc to 620 emu/cc and high magnetic anisotropy (Ku ~ 3 × 105 J m−3) even after annealing at temperatures as high as 400 °C. Successive domain mapping by magnetic force microscopy revealed characteristics of multi-domains stripe that feature at all stages of annealing except at 500 °C, attributed to the loss of PMA, driven by interfacial diffusion. High frequency broadband ferromagnetic resonance measurements showed little effect of annealing on intrinsic damping parameter (α = 0.019–0.024) while inhomogeneous linewidth broadening varied without a clear trend. These results are discussed considering crystallographic modifications and it was found that fcc (1 1 1) texture was retained in the samples until 400 °C post annealing. The retention of a high anisotropy, high magnetization and low damping constant after high temperature annealing makes these Co/Ni multilayers suitable for designing spin torque based memory devices.

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Section: Introductionmentioning

confidence: 99%

[Co/Ni] multilayers with robust post-annealing performance for spintronics device applications

Gupta¹,

Sbiaa²,

Bahri³

et al. 2018

J. Phys. D: Appl. Phys.

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“…Perpendicular magnetic anisotropy (PMA) materials with low saturation magnetization (Ms), low damping constant (α), and high spin polarization (P) are desired to meet the above-mentioned properties [1,2]. So far, several types of PMA materials such as Co/(Pt, Pd, Ni) multilayers [3][4][5][6][7][8], (Fe, Co)Pt ordered alloys [9,10], and TbFeCo and GdCoFe rare-earth alloys [11,12] have been extensively studied. Although many types of materials have been investigated, the window is still open for researchers to fabricate new materials for STT-MRAM applications.…”

Section: Introductionmentioning

confidence: 99%

Structural and magnetic properties of cubic and tetragonal Heusler alloy bilayers

et al. 2016

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Different cubic Co-based Heusler alloys-Co 2 FeAl (CFA), Co 2 FeSi (CFS), Co 2 MnAl (CMA), and Co 2 MnSi (CMS)-were grown epitaxially on tetragonal Heusler-like D0 22-MnGa at different annealing temperatures (T a) in the form of Heusler (20 nm)/MnGa (30 nm) bilayers. The CMA/MnGa bilayer showed the largest critical temperature (450 • C), indicating good structural stability against interdiffusion. The experimental results showed an easier interdiffusion of the Fe and Si elements than of Mn and Al. An inverted hysteresis loop was observed in a polar magneto-optical Kerr effect (P-MOKE) measurement for the CFS/MnGa, CMA/MnGa, and CMS/MnGa bilayers. This is one piece of evidence for the existence of the antiferromagnetic (AFM) interfacial exchange coupling (J ex). We evaluated J ex for the Heusler/MnGa bilayers annealed at different temperatures. J ex changed from ferromagnetic (FM) to AFM after annealing at 300 • C for the CFA/MnGa bilayer. Other bilayers showed only AFM coupling. The strongest J ex value of approximately-3.2 erg/cm 2 was obtained for the CMS/MnGa bilayer annealed at 400 • C. It was found that the tendency of the Mn and Si elements to make AFM J ex in the Heusler/MnGa bilayers interfaces is larger than that of Fe and Al.

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“…The requirements on PMA electrodes include high thermal stability at reduced dimensions, low switching current and high TMR all at the same time. Various PMA materials have been studied for STT-MRAM electrodes, including (Co,Fe)/(Pt,Pd) multilayers [6][7][8], L1 0 -ordered (Co,Fe)Pt alloys [9][10][11], rareearth/transitional-metal (RE/TM) alloys [12,13], ultrathin CoFeB [14] and CoFeAl [15,16] films, and tetragonal manganese alloys such as Mn 3 Ga [17]. Despite of intensive research none of these materials satisfy strict requirements that would allow STT-MRAM to replace conventional memory today.…”

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confidence: 99%

Brillouin zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in aCo(0001)/h -BN/Co(0001)magnetic tunnel junction

2015

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The 'Brillouin zone spin filtering' mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJ) and studied on an example of the MTJ with hcp Co electrodes and hexagonal BN (h-BN) spacer. Our calculations based on local density approximation of density functional theory (LDA-DFT) for Co(0001)/h-BN/Co(0001) MTJ predict high TMR in this device due to Brillouin zone filtering mechanism. Owning to the specific complex band structure of the h-BN the spin-dependent tunneling conductance of the system is ultra-sensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport propertied of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and p-doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory (STT-MRAM).

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MTJ Elements With MgO Barrier Using RE-TM Amorphous Layers for Perpendicular MRAM

Cited by 21 publications

References 7 publications

[Co/Ni] multilayers with robust post-annealing performance for spintronics device applications

[Co/Ni] multilayers with robust post-annealing performance for spintronics device applications

Structural and magnetic properties of cubic and tetragonal Heusler alloy bilayers

Brillouin zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in aCo(0001)/h -BN/Co(0001)magnetic tunnel junction

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