1
|
Hussien MAM, Ukpong AM. Quantum Phase Transition in the Spin Transport Properties of Ferromagnetic Metal-Insulator-Metal Hybrid Materials. NANOMATERIALS 2022; 12:nano12111836. [PMID: 35683692 PMCID: PMC9182424 DOI: 10.3390/nano12111836] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/20/2022] [Accepted: 05/23/2022] [Indexed: 01/25/2023]
Abstract
Perpendicular magnetic tunnel junctions provide a technologically important design platform for studying metal-insulator-metal heterostructure materials. Accurate characterization of the sensitivity of their electronic structure to proximity coupling effects based on first-principles calculations is key in the fundamental understanding of their emergent collective properties at macroscopic scales. Here, we use an effective field theory that combines ab initio calculations of the electronic structure within density functional theory with the plane waves calculation of the spin polarised conductance to gain insights into the proximity effect induced magnetoelectric couplings that arise in the transport of spin angular momentum when a monolayer tunnel barrier material is integrated into the magnetic tunnel junction. We find that the spin density of states exhibits a discontinuous change from half-metallic to the metallic character in the presence of monolayer hexagonal boron nitride when the applied electric field reaches a critical amplitude, and this signals a first order transition in the transport phase. This unravels an electric-field induced quantum phase transition in the presence of a monolayer hexagonal boron nitride tunnel barrier quite unlike molybdenum disulphide. The role of the applied electric field in the observed phase transition is understood in terms of the induced spin-flip transition and the charge transfer at the constituent interfaces. The results of this study show that the choice of the tunnel barrier layer material plays a nontrivial role in determining the magnetoelectric couplings during spin tunnelling under external field bias.
Collapse
Affiliation(s)
- Musa A. M. Hussien
- Theoretical and Computational Condensed Matter and Materials Physics Group (TCCMMP), School of Chemistry and Physics, University of KwaZulu-Natal, Pietermaritzburg 3201, South Africa;
| | - Aniekan Magnus Ukpong
- Theoretical and Computational Condensed Matter and Materials Physics Group (TCCMMP), School of Chemistry and Physics, University of KwaZulu-Natal, Pietermaritzburg 3201, South Africa;
- National Institute for Theoretical and Computational Sciences (NITheCS), Pietermaritzburg 3201, South Africa
- Correspondence: ; Tel.: +27-33-260-5875; Fax: +27-031-260-3091
| |
Collapse
|
2
|
An electrically reconfigurable logic gate intrinsically enabled by spin-orbit materials. Sci Rep 2017; 7:15358. [PMID: 29127296 PMCID: PMC5681507 DOI: 10.1038/s41598-017-14783-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 10/16/2017] [Indexed: 11/25/2022] Open
Abstract
The spin degree of freedom in magnetic devices has been discussed widely for computing, since it could significantly reduce energy dissipation, might enable beyond Von Neumann computing, and could have applications in quantum computing. For spin-based computing to become widespread, however, energy efficient logic gates comprising as few devices as possible are required. Considerable recent progress has been reported in this area. However, proposals for spin-based logic either require ancillary charge-based devices and circuits in each individual gate or adopt principals underlying charge-based computing by employing ancillary spin-based devices, which largely negates possible advantages. Here, we show that spin-orbit materials possess an intrinsic basis for the execution of logic operations. We present a spin-orbit logic gate that performs a universal logic operation utilizing the minimum possible number of devices, that is, the essential devices required for representing the logic operands. Also, whereas the previous proposals for spin-based logic require extra devices in each individual gate to provide reconfigurability, the proposed gate is ‘electrically’ reconfigurable at run-time simply by setting the amplitude of the clock pulse applied to the gate. We demonstrate, analytically and numerically with experimentally benchmarked models, that the gate performs logic operations and simultaneously stores the result, realizing the ‘stateful’ spin-based logic scalable to ultralow energy dissipation.
Collapse
|
3
|
Ultrafast electronic response of graphene to a strong and localized electric field. Nat Commun 2016; 7:13948. [PMID: 28000666 PMCID: PMC5187589 DOI: 10.1038/ncomms13948] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 11/15/2016] [Indexed: 12/18/2022] Open
Abstract
The way conduction electrons respond to ultrafast external perturbations in low dimensional materials is at the core of the design of future devices for (opto)electronics, photodetection and spintronics. Highly charged ions provide a tool for probing the electronic response of solids to extremely strong electric fields localized down to nanometre-sized areas. With ion transmission times in the order of femtoseconds, we can directly probe the local electronic dynamics of an ultrathin foil on this timescale. Here we report on the ability of freestanding single layer graphene to provide tens of electrons for charge neutralization of a slow highly charged ion within a few femtoseconds. With values higher than 1012 A cm−2, the resulting local current density in graphene exceeds previously measured breakdown currents by three orders of magnitude. Surprisingly, the passing ion does not tear nanometre-sized holes into the single layer graphene. We use time-dependent density functional theory to gain insight into the multielectron dynamics.
Graphene has so far demonstrated remarkable properties, making it increasingly interesting for ultrafast electronic applications. Here, the authors show that, when probed by a highly charged ion, freestanding graphene is able to provide dozens of electrons for ion neutralization within a few femtoseconds.
Collapse
|
4
|
Sakai S, Majumdar S, Popov ZI, Avramov PV, Entani S, Hasegawa Y, Yamada Y, Huhtinen H, Naramoto H, Sorokin PB, Yamauchi Y. Proximity-Induced Spin Polarization of Graphene in Contact with Half-Metallic Manganite. ACS NANO 2016; 10:7532-7541. [PMID: 27438899 DOI: 10.1021/acsnano.6b02424] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The role of proximity contact with magnetic oxides is of particular interest from the expectations of the induced spin polarization and weak interactions at the graphene/magnetic oxide interfaces, which would allow us to achieve efficient spin-polarized injection in graphene-based spintronic devices. A combined approach of topmost-surface-sensitive spectroscopy utilizing spin-polarized metastable He atoms and ab initio calculations provides us direct evidence for the magnetic proximity effect in the junctions of single-layer graphene and half-metallic manganite La0.7Sr0.3MnO3 (LSMO). It is successfully demonstrated that in the graphene/LSMO junctions a sizable spin polarization is induced at the Fermi level of graphene in parallel to the spin polarization direction of LSMO without giving rise to a significant modification in the π band structure.
Collapse
Affiliation(s)
- Seiji Sakai
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology QST , 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
- National Institute for Materials Science , Tsukuba, Ibaraki 305-0047, Japan
- Institute of Applied Physics, University of Tsukuba , 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Sayani Majumdar
- Department of Applied Physics, Aalto University School of Science , FI-00076 Aalto, Finland
| | - Zakhar I Popov
- National University of Science and Technology MISiS , 4 Leninskiy Prospekt, Moscow 119049, Russian Federation
| | - Pavel V Avramov
- Department of Chemistry, College of Natural Sciences, Kyungpook National University , Daegu 702-701, Republic of Korea
| | - Shiro Entani
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology QST , 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Yuri Hasegawa
- Institute of Applied Physics, University of Tsukuba , 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Yoichi Yamada
- Institute of Applied Physics, University of Tsukuba , 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Hannu Huhtinen
- Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku , 20014, Turku, Finland
| | - Hiroshi Naramoto
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology QST , 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
| | - Pavel B Sorokin
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology QST , 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
- National University of Science and Technology MISiS , 4 Leninskiy Prospekt, Moscow 119049, Russian Federation
- Technological Institute of Superhard and Novel Carbon Materials , 7a Centralnaya Street, Troitsk, Moscow 142190, Russian Federation
| | - Yasushi Yamauchi
- Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology QST , 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan
- National Institute for Materials Science , Tsukuba, Ibaraki 305-0047, Japan
| |
Collapse
|
5
|
Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy. MATERIALS 2016; 9:ma9010041. [PMID: 28787842 PMCID: PMC5456535 DOI: 10.3390/ma9010041] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 12/23/2015] [Accepted: 01/06/2016] [Indexed: 11/17/2022]
Abstract
Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ) becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM) for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high scalability, and easy integration into conventional complementary metal oxide semiconductor (CMOS) circuits. However, this device suffers from a number of failure issues, such as large process variation and tunneling barrier breakdown. The large process variation is an intrinsic issue for PMA-MTJ as it is based on the interfacial effects between ultra-thin films with few layers of atoms; the tunneling barrier breakdown is due to the requirement of an ultra-thin tunneling barrier (e.g., <1 nm) to reduce the resistance area for the spin transfer torque switching in the nanopillar. These failure issues limit the research and development of STT-MRAM to widely achieve commercial products. In this paper, we give a full analysis of failure mechanisms for PMA-MTJ and present some eventual solutions from device fabrication to system level integration to optimize the failure issues.
Collapse
|