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Suzuki, Kazuya; Mizukami, Shigemi*
AIP Advances (Internet), 13(3), p.035225_1 - 035225_6, 2023/03
Times Cited Count：1 Percentile：49.29(Nanoscience & Nanotechnology)We studied MgO barrier magnetic tunnel junctions (MTJs) comprising perpendicularly magnetized MnGa and FeCoB electrodes. In those perpendicular (
-) MTJs, we utilized thin metastable bcc CoMn alloys for an interlayer between MnGa and MgO to enhance the tunnel magnetoresistance (TMR). Moreover, we investigated the effect of a thin Mg interlayer between MnGa and CoMn. Owing to the interlayer engineering, we achieved a TMR ratio over 100%, the highest value observed for -MTJs with a tetragonal MnGa electrode. Our study contributes to the further development of spintronic devices using -MTJs with various Mn-based tetragonal alloy electrodes.
Okabayashi, Jun*; Suzuki, Kazuya; Mizukami, Shigemi*
Journal of Magnetism and Magnetic Materials, 564, Part2, p.170163_1 - 170163_5, 2022/12
Times Cited Count：1 Percentile：14.38(Materials Science, Multidisciplinary)The magnetic atom diffusion at the interface between CoMn alloy and MnGa layer with annealing is studied using X-ray magnetic circular dichroism (XMCD) analysis. We found that the spins in bcc CoMn are coupled parallel to those in perpendicularly magnetized MnGa layer under the as-grown conditions, while the post annealing modulates the interfacial magnetic coupling to antiferromagnetic in Co. The elementspecific hysteresis curves at each absorption edge revealed the large coercive fields in Mn and Co through the exchange coupling with MnGa. After the annealing process, the changes of XMCD spectral line shapes are related to the interfacial reactions promoting the formation of Mn and Co
MnGa layers, which is deduced from the analysis oftransmission electron microscopy. The interfacial diffusion of Mn atoms modulates the magnetic exchange coupling between Mn and Co sites and reverses the direction of perpendicular magnetization.
Suzuki, Kazuya; Ichinose, Tomohiro*; Iihama, Satoshi*; Momma, Ren*; Kamata, Naoki*; Mizukami, Shigemi*
no journal, ,
Perpendicular magnetic tunnel junctions (p-MTJs) are key devices for rich applications such as magneto-resistive random access memory, magnetic sensor, and high frequency devices. Not only do they be required to have proper magnetic properties for the applications, but they also need to have a high TMR ratio at operating temperatures. Tetragonal Mn-based alloys are one of distinctive and attractive perpendicular magnetic materials as the electrode materials for p-MTJs because of their small saturation magnetization, large coercivity, large perpendicular magnetic anisotropy, and small Gilbert damping factor. However, the p-MTJs utilizing Mn-based alloy as the ferromagnetic electrode have only exhibited small TMR at room temperature, still maximum of 60% even if FeCo interlayers were used. We have recently focused on bcc-Co based alloys as the interlayer material for MnGa-based MTJs in order to enhance further TMR. In this presentation, we demonstrate the p-MTJs utilizing bcc-CoMn interlayers and their TMR properties, and we briefly introduce recent progress for MnGa-based p-MTJs, as well.
Suzuki, Kazuya; Mizukami, Shigemi*
no journal, ,
Perpendicular magnetic tunnel junctions (p-MTJs) utilizing tetragonal Mn-based alloy thin films are one of the attractive p-MTJs for magnetic random access memory, advanced THz applications and sensors1,2. One of the important performances for p-MTJs can be high tunnel magnetoresistance at room temperature. Although past studies have been reported the small TMR ratio of p-MTJ using Mn-based alloy electrode, recently, we achieved high TMR of 80% using antiferromagnetically coupled ultra-thin MnGa/CoMn electrodes3. In this study, we report achieving over 100% at room temperature by the introduction of ultrathin insertion layer in the MnGa/CoMn interface.
Kamata, Naoki*; Mizukami, Shigemi*; Suzuki, Kazuya
no journal, ,
Perpendicularly magnetized tetragonal Mn-based alloy thin films are attractive materials as a ferromagnetic electrodes of perpendicular magnetic tunnel junctions (p-MTJs). In this study, we demonstrate the p-MTJs using L10-MnGa ultrathin electrodes grown on the sapphire(r-plane) substrate. We succeeded the growth of single crystalline L10-MnGa ultrathin films on the sapphire(r-plane) substrate by introducing the bcc-Ta/Cr/CoGa hybrid buffer layers between substrate and MnGa layers. In addition, the p-MTJs grown on sapphire substrate exhibited clear TMR of 6-7% at room temperature. These results suggests that new growth technique of single crystalline MnGa ultrathin film will open the development of single crystalline MnGa-based spintronics devices.
