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Chaves JF, Noris LF, Yokoyama E, Osorio G. FG, Mendoza LAF, Araujo JFDF. Multisensor Magnetic Scanning Microscope for Remanent Magnetic Field Measurements. SENSORS (BASEL, SWITZERLAND) 2024; 24:2294. [PMID: 38610505 PMCID: PMC11013988 DOI: 10.3390/s24072294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 03/27/2024] [Accepted: 04/02/2024] [Indexed: 04/14/2024]
Abstract
Magnetic Scanning Microscopy (MSM) emerged with the aim of allowing the visualization of magnetic fields of a sample or material through scanning and proved particularly useful for geology, biomedicine, characterization of magnetic materials, and in the steel industry. In this regard, the reading system of an MSM was modified using a μ-metal magnetic shielding structure to analyze remanent fields. The MSM was adapted to perform readings using two different types of sensors. The sensitive area of the sensors was evaluated, and the HQ-0811 (AKM-Asahi KaseiTM Microdevices) and STJ-010 (Micro MagneticsTM) sensors were chosen, with the HQ-0811 standardized on Printed Circuit Boards (PCBs) to facilitate handling and increase the system's robustness. In the shielded chamber, two piezoelectric ANC-150 stepper motors (Attocube Systems) were used, arranged planarly, to allow the movement of the analyzed samples under the mounted sensors. To acquire data from the sensors, the Precision Current Source Model 6220 and the Nanovoltmeter Model 2182A (both from Keithley) were used, along with Keithley's Delta-Mode integrated system. To analyze the system's effectiveness, three distinct samples were analyzed for calibration, and a MATLAB program was written to analyze the images and extract the material's magnetization. Additionally, a rock sample from the Parnaíba Basin was mapped to demonstrate the system's capabilities.
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Affiliation(s)
- João F. Chaves
- Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil; (J.F.C.); (L.F.N.); (F.G.O.G.)
| | - Leosdan F. Noris
- Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil; (J.F.C.); (L.F.N.); (F.G.O.G.)
| | - Elder Yokoyama
- Department of Geosciences, University of Brasília, Brasília 70910-900, Brazil;
| | - Fredy G. Osorio G.
- Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil; (J.F.C.); (L.F.N.); (F.G.O.G.)
| | - Leonardo A. F. Mendoza
- Department of Electrical Engineering, State University of Rio de Janeiro-UERJ, Rio de Janeiro 20550-900, Brazil;
| | - Jefferson F. D. F. Araujo
- Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil; (J.F.C.); (L.F.N.); (F.G.O.G.)
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2
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Miura Y, Okabayashi J. Understanding magnetocrystalline anisotropy based on orbital and quadrupole moments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:473001. [PMID: 36137512 DOI: 10.1088/1361-648x/ac943f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Understanding magnetocrystalline anisotropy (MCA) is fundamentally important for developing novel magnetic materials. Therefore, clarifying the relationship between MCA and local physical quantities observed by spectroscopic measurements, such as the orbital and quadrupole moments, is necessary. In this review, we discuss MCA and the distortion effects in magnetic materials with transition metals (TMs) based on the orbital and quadrupole moments, which are related to the spin-conserving and spin-flip terms in the second-order perturbation calculations, respectively. We revealed that orbital moment stabilized the spin moment in the direction of the larger orbital moment, while the quadrupole moment stabilized the spin moment along the longitudinal direction of the spin-density distribution. The MCA of the magnetic materials with TMs and their interfaces can be determined from the competition between these two contributions. We showed that the perpendicular MCA of the face-centered cubic Ni with tensile tetragonal distortion arose from the orbital moment anisotropy, whereas that of Mn-Ga alloys originated from the quadrupole moment of spin density. In contrast, in the Co/Pd(111) multilayer and Fe/MgO(001), both the orbital moment anisotropy and quadrupole moment of spin density at the interfaces contributed to the perpendicular MCA. Understanding the MCA of magnetic materials and interfaces based on orbital and quadrupole moments is essential to design MCA of novel magnetic applications.
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Affiliation(s)
- Yoshio Miura
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba 305-0047, Japan
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560-8531, Japan
| | - Jun Okabayashi
- Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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3
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Fecher GH. Discontinuity in the Electronic Structure and Magnetic Order of β-Co 1+xGa 1-x. MATERIALS (BASEL, SWITZERLAND) 2022; 15:5523. [PMID: 36013659 PMCID: PMC9413009 DOI: 10.3390/ma15165523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/09/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
The present work reports on the calculated electronic and magnetic structure of the binary Co-Ga system at high Co content. β-CoGa adopts a simple cubic CsCl type structure. Well-ordered CoGa does not exhibit collective magnetism but is a paramagnetic, metallic compound. Neither Co nor Ga deficiency induces magnetic order; however, ferromagnetism is observed for Co-Ga anti-site disorder. The magnetic moment per cell increases by up to approximately 1.2 μB in the completely disordered body-centered cubic structure. With increasing Co content, Co1+xGa1-x maintains the CsCl type structure and becomes ferromagnetic. Most importantly, a discontinuity of the magnetic order with composition is observed at about 10% excess Co, where a change from a low magnetic moment state to a high moment state is observed. This is accompanied by a change in the electronic structure and transport properties. The discontinuity is forced by the increasing exchange splitting related to the localized moment of the additional Co atoms that replace Ga. Subsequently, the magnetic moment increases continuously up to 2.5 μB for x=0.6. For x≳0.6, the structure changes to a face-centered cubic structure with random site occupation and the magnetic moment further increases. Above the magnetic discontinuity, the Curie temperature increases linearly with the Co content from the onset of ferromagnetism, until it reaches its maximum in pure Co.
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Affiliation(s)
- Gerhard H Fecher
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
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Elphick K, Frost W, Samiepour M, Kubota T, Takanashi K, Sukegawa H, Mitani S, Hirohata A. Heusler alloys for spintronic devices: review on recent development and future perspectives. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2021; 22:235-271. [PMID: 33828415 PMCID: PMC8009123 DOI: 10.1080/14686996.2020.1812364] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 08/17/2020] [Accepted: 08/17/2020] [Indexed: 05/14/2023]
Abstract
Heusler alloys are theoretically predicted to become half-metals at room temperature (RT). The advantages of using these alloys are good lattice matching with major substrates, high Curie temperature above RT and intermetallic controllability for spin density of states at the Fermi energy level. The alloys are categorised into half- and full-Heusler alloys depending upon the crystalline structures, each being discussed both experimentally and theoretically. Fundamental properties of ferromagnetic Heusler alloys are described. Both structural and magnetic characterisations on an atomic scale are typically carried out in order to prove the half-metallicity at RT. Atomic ordering in the films is directly observed by X-ray diffraction and is also indirectly probed via the temperature dependence of electrical resistivity. Element specific magnetic moments and spin polarisation of the Heusler alloy films are directly measured using X-ray magnetic circular dichroism and Andreev reflection, respectively. By employing these ferromagnetic alloy films in a spintronic device, efficient spin injection into a non-magnetic material and large magnetoresistance are also discussed. Fundamental properties of antiferromagnetic Heusler alloys are then described. Both structural and magnetic characterisations on an atomic scale are shown. Atomic ordering in the Heusler alloy films is indirectly measured by the temperature dependence of electrical resistivity. Antiferromagnetic configurations are directly imaged by X-ray magnetic linear dichroism and polarised neutron reflection. The applications of the antiferromagnetic Heusler alloy films are also explained. The other non-magnetic Heusler alloys are listed. A brief summary is provided at the end of this review.
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Affiliation(s)
- Kelvin Elphick
- Department of Electronic Engineering, University of York, York, UK
| | - William Frost
- Department of Electronic Engineering, University of York, York, UK
| | - Marjan Samiepour
- Department of Electronic Engineering, University of York, York, UK
- Seagate Technology,1 Disc Drive, Springtown Industrial Estate, Londonderry, Northern Ireland
| | - Takahide Kubota
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, Japan
| | - Koki Takanashi
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, Japan
- Center for Science and Innovation in Spintronics, Core Research Cluster, Tohoku University, Sendai, Japan
| | - Hiroaki Sukegawa
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Seiji Mitani
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan
- Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan
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Okabayashi J, Miura Y, Kota Y, Z Suzuki K, Sakuma A, Mizukami S. Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys. Sci Rep 2020; 10:9744. [PMID: 32546779 PMCID: PMC7297735 DOI: 10.1038/s41598-020-66432-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 05/07/2020] [Indexed: 11/25/2022] Open
Abstract
Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn3− δ Ga ordered alloys is investigated to resolve antiparallel-coupled Mn sites using x-ray magnetic circular and linear dichroism (XMCD/XMLD) and a first-principles calculation. We found that the contribution of orbital magnetic moments in PMA is small from XMCD and that the finite quadrupole-like orbital distortion through spin-flipped electron hopping is dominant from XMLD and theoretical calculations. These findings suggest that the spin-flipped orbital quadrupole formations originate from the PMA in Mn3− δ Ga and bring the paradigm shift in the researches of PMA materials using x-ray magnetic spectroscopies.
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Affiliation(s)
- Jun Okabayashi
- Research Center for Spectrochemistry, The University of Tokyo, 113-0033, Tokyo, Japan.
| | - Yoshio Miura
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
| | - Yohei Kota
- National Institute of Technology, Fukushima College, Iwaki, Fukushima, 970-8034, Japan
| | - Kazuya Z Suzuki
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan
| | - Akimasa Sakuma
- Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Department of Applied Physics, Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
| | - Shigemi Mizukami
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
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Suzuki KZ, Kimura S, Kubota H, Mizukami S. Magnetic Tunnel Junctions with a Nearly Zero Moment Manganese Nanolayer with Perpendicular Magnetic Anisotropy. ACS APPLIED MATERIALS & INTERFACES 2018; 10:43305-43310. [PMID: 30520620 DOI: 10.1021/acsami.8b15606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A magnetic nanolayer with a perpendicular magnetic easy axis and negligible magnetization is demonstrated. Even though a manganese metal is antiferromagnetic in bulk form, a few manganese monolayers grown on a paramagnetic ordered alloy template and capped by an oxide layer exhibit a strong perpendicular magnetic anisotropy field exceeding 19 T as well as a negligible magnetization of 25 kA/m. The nanolayer shows tunnel magnetoresistance. Moreover, the perpendicular magnetic anisotropy for the nanolayer can be reduced by applying an electric voltage. These findings will provide new insight into a creation of new nanolayer magnets.
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Affiliation(s)
| | | | - Hitoshi Kubota
- National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center , Tsukuba 305-8568 , Japan
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7
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Chen T, Wang J, Cheng Z, Wang X, Chen H. Structural, electronic and magnetic properties of Mn xGa/Co 2MnSi (x = 1, 3) bilayers. Sci Rep 2018; 8:16530. [PMID: 30410085 PMCID: PMC6224613 DOI: 10.1038/s41598-018-34881-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 10/16/2018] [Indexed: 11/09/2022] Open
Abstract
Directly coupled hard and soft ferromagnets were popularly used as the hybridized electrodes to enhance tunnel magnetoresistance (TMR) ratio in the perpendicular magnetic tunnel junction (pMTJ). In this paper, we employ the density functional theory (DFT) with general gradient approximation (GGA) to investigate the interfacial structure and magnetic behavior of tetragonal Heusler-type MnGa (MG)/L21-Co2MnSi (CMS) Heusler alloy bilayers with the MnGa being D022-MnGa alloy (Mn3Ga) and L10-MnGa alloy (MnGa). The MM-MS_B interface with the bridge (B) connection of MnMn termination (MM) of D022- and L10-MnGa layers to MnSi termination (MS) of CMS layers is found to be most stable in the energy point of view. Also, a strong antiferromagnetic coupling and relatively higher spin polarization can be observed in the MM-MS_B interface. Further, a remarkable potential difference to derive electrons to transfer from MG layer to CMS layer appears at the interface. These theoretical results indicate that the MG/CMS bilayers are promising candidates as coupled composites, and moreover, the D022-MG/CMS bilayer is better than L10-MG/CMS bilayer due to its larger spin polarization and built-in field at the interface.
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Affiliation(s)
- Ting Chen
- School of Physical Science and Technology, Southwest University, Chongqing, 400715, People's Republic of China
| | - Junhao Wang
- School of Physical Science and Technology, Southwest University, Chongqing, 400715, People's Republic of China
| | - Zhenxiang Cheng
- Institute for Superconducting & Electronic Materials (ISEM), University of Wollongong, Wollongong, 2500, Australia
| | - Xiaotian Wang
- School of Physical Science and Technology, Southwest University, Chongqing, 400715, People's Republic of China
| | - Hong Chen
- School of Physical Science and Technology, Southwest University, Chongqing, 400715, People's Republic of China.
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Chiral domain wall motion in unit-cell thick perpendicularly magnetized Heusler films prepared by chemical templating. Nat Commun 2018; 9:4653. [PMID: 30405099 PMCID: PMC6220290 DOI: 10.1038/s41467-018-07091-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 10/01/2018] [Indexed: 11/08/2022] Open
Abstract
Heusler alloys are a large family of compounds with complex and tunable magnetic properties, intimately connected to the atomic scale ordering of their constituent elements. We show that using a chemical templating technique of atomically ordered X'Z' (X' = Co; Z' = Al, Ga, Ge, Sn) underlayers, we can achieve near bulk-like magnetic properties in tetragonally distorted Heusler films, even at room temperature. Excellent perpendicular magnetic anisotropy is found in ferrimagnetic X3Z (X = Mn; Z = Ge, Sn, Sb) films, just 1 or 2 unit-cells thick. Racetracks formed from these films sustain current-induced domain wall motion with velocities of more than 120 m s-1, at current densities up to six times lower than conventional ferromagnetic materials. We find evidence for a significant bulk chiral Dzyaloshinskii-Moriya exchange interaction, whose field strength can be systematically tuned by an order of magnitude. Our work is an important step towards practical applications of Heusler compounds for spintronic technologies.
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Hirohata A, Frost W, Samiepour M, Kim JY. Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions. MATERIALS (BASEL, SWITZERLAND) 2018; 11:E105. [PMID: 29324709 PMCID: PMC5793603 DOI: 10.3390/ma11010105] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 01/04/2018] [Accepted: 01/05/2018] [Indexed: 11/24/2022]
Abstract
For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch. In this review, recent development in perpendicularly-magnetised Heusler-alloy films is overviewed and their magnetoresistive junctions are discussed. Especially, focus is given to binary Heusler alloys by replacing the second element in the ternary Heusler alloys with the third one, e.g., MnGa and MnGe, and to interfacially-induced anisotropy by attaching oxides and metals with different lattice constants to the Heusler alloys. These alloys can improve the performance of spintronic devices with higher recording capacity.
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Affiliation(s)
- Atsufumi Hirohata
- Department of Electronic Engineering, University of York, York YO10 5DD, UK.
| | - William Frost
- Department of Electronic Engineering, University of York, York YO10 5DD, UK.
| | - Marjan Samiepour
- Department of Electronic Engineering, University of York, York YO10 5DD, UK.
| | - Jun-Young Kim
- Department of Physics, University of York, York YO10 5DD, UK.
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10
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Mao S, Lu J, Zhao X, Wang X, Wei D, Liu J, Xia J, Zhao J. MnGa-based fully perpendicular magnetic tunnel junctions with ultrathin Co 2MnSi interlayers. Sci Rep 2017; 7:43064. [PMID: 28233780 PMCID: PMC5324047 DOI: 10.1038/srep43064] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 01/18/2017] [Indexed: 11/13/2022] Open
Abstract
Because tetragonal structured MnGa alloy has intrinsic (not interface induced) giant perpendicular magnetic anisotropy (PMA), ultra-low damping constant and high spin polarization, it is predicted to be a kind of suitable magnetic electrode candidate in the perpendicular magnetic tunnel junction (p-MTJ) for high density spin transfer torque magnetic random access memory (STT-MRAM) applications. However, p-MTJs with both bottom and top MnGa electrodes have not been achieved yet, since high quality perpendicular magnetic MnGa films can hardly be obtained on the MgO barrier due to large lattice mismatch and surface energy difference between them. Here, a MnGa-based fully p-MTJ with the structure of MnGa/Co2MnSi/MgO/Co2MnSi/MnGa is investigated. As a result, the multilayer is with high crystalline quality, and both the top and bottom MnGa electrodes show well PMA. Meanwhile, a distinct tunneling magnetoresistance (TMR) ratio of 65% at 10 K is achieved. Ultrathin Co2MnSi films are used to optimize the interface quality between MnGa and MgO barrier. A strong antiferromagnetic coupling in MnGa/Co2MnSi bilayer is confirmed with the interfacial exchange coupling constant of −5erg/cm2. This work proposes a novel p-MTJ structure for the future STT-MRAM progress.
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Affiliation(s)
- Siwei Mao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Jun Lu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Xupeng Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Xiaolei Wang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Dahai Wei
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Jian Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Jianbai Xia
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912,Beijing 100083, China
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