1
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Kumari P, Majumder S, Kar S, Rani S, Nair AK, Kumari K, Kamalakar MV, Ray SJ. An all phosphorene lattice nanometric spin valve. Sci Rep 2024; 14:9138. [PMID: 38644366 PMCID: PMC11033266 DOI: 10.1038/s41598-024-58589-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Accepted: 04/01/2024] [Indexed: 04/23/2024] Open
Abstract
Phosphorene is a unique semiconducting two-dimensional platform for enabling spintronic devices integrated with phosphorene nanoelectronics. Here, we have designed an all phosphorene lattice lateral spin valve device, conceived via patterned magnetic substituted atoms of 3d-block elements at both ends of a phosphorene nanoribbon acting as ferromagnetic electrodes in the spin valve. Through First-principles based calculations, we have extensively studied the spin-dependent transport characteristics of the new spin valve structures. Systematic exploration of the magnetoresistance (MR) of the spin valve for various substitutional atoms and bias voltage resulted in a phase diagram offering a colossal MR for V and Cr-substitutional atoms. Such MR can be directly attributed to their specific electronic structure, which can be further tuned by a gate voltage, for electric field controlled spin valves. The spin-dependent transport characteristics here reveal new features such as negative conductance oscillation and switching of the sign of MR due to change in the majority spin carrier type. Our study creates possibilities for the design of nanometric spin valves, which could enable integration of memory and logic elements for all phosphorene 2D processors.
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Affiliation(s)
- P Kumari
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - S Majumder
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - S Kar
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - S Rani
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - A K Nair
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - K Kumari
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - S J Ray
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India.
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2
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R RK, Kalaboukhov A, Weng YC, Rathod KN, Johansson T, Lindblad A, Kamalakar MV, Sarkar T. Vacancy-Engineered Nickel Ferrite Forming-Free Low-Voltage Resistive Switches for Neuromorphic Circuits. ACS Appl Mater Interfaces 2024; 16:19225-19234. [PMID: 38579143 DOI: 10.1021/acsami.4c01501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/07/2024]
Abstract
Innovations in resistive switching devices constitute a core objective for the development of ultralow-power computing devices. Forming-free resistive switching is a type of resistive switching that eliminates the need for an initial high voltage for the formation of conductive filaments and offers promising opportunities to overcome the limitations of traditional resistive switching devices. Here, we demonstrate mixed charge state oxygen vacancy-engineered electroforming-free resistive switching in NiFe2O4 (NFO) thin films, fabricated as asymmetric Ti/NFO/Pt heterostructures, for the first time. Using pulsed laser deposition in a controlled oxygen atmosphere, we tune the oxygen vacancies together with the cationic valence state in the nickel ferrite phase, with the latter directly affecting the charge state of the oxygen vacancies. The structural integrity and chemical composition of the films are confirmed by X-ray diffraction and hard X-ray photoelectron spectroscopy, respectively. Electrical transport studies reveal that resistive switching characteristics in the films can be significantly altered by tuning the amount and charge state of the oxygen vacancy concentration during the deposition of the films. The resistive switching mechanism is seen to depend upon the migration of both singly and doubly charged oxygen vacancies formed as a result of changes in the nickel valence state and the consequent formation/rupture of conducting filaments in the switching layer. This is supported by the existence of an optimum oxygen vacancy concentration for efficient low-voltage resistive switching, below or above which the switching process is inhibited. Along with the filamentary switching mechanism, the Ti top electrode also enhances the resistive switching performance due to interfacial effects. Time-resolved measurements on the devices display both long- and short-term potentiation in the optimized vacancy-engineered NFO resistive switches, ideal for solid-state synapses achieved in a single system. Our work on correlated oxide forming-free resistive switches holds significant potential for CMOS-compatible low-power, nonvolatile resistive memory and neuromorphic circuits.
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Affiliation(s)
- Rajesh Kumar R
- Division of Solid State Physics, Department of Materials Science and Engineering, Uppsala University, Uppsala SE-751 03, Sweden
| | - Alexei Kalaboukhov
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Yi-Chen Weng
- Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala SE-751 20, Sweden
| | - K N Rathod
- Division of Solid State Physics, Department of Materials Science and Engineering, Uppsala University, Uppsala SE-751 03, Sweden
| | - Ted Johansson
- Division of Solid-State Electronics, Department of Electrical Engineering, Uppsala University, Uppsala SE-751 21, Sweden
| | - Andreas Lindblad
- Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala SE-751 20, Sweden
| | - M Venkata Kamalakar
- Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Uppsala SE-751 20, Sweden
| | - Tapati Sarkar
- Division of Solid State Physics, Department of Materials Science and Engineering, Uppsala University, Uppsala SE-751 03, Sweden
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3
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Belotcerkovtceva D, Nameirakpam H, Datt G, Noumbe U, Kamalakar MV. High current treated-passivated graphene (CTPG) towards stable nanoelectronic and spintronic circuits. Nanoscale Horiz 2024; 9:456-464. [PMID: 38214968 DOI: 10.1039/d3nh00338h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Achieving enhanced and stable electrical quality of scalable graphene is crucial for practical graphene device applications. Accordingly, encapsulation has emerged as an approach for improving electrical transport in graphene. In this study, we demonstrate high-current treatment of graphene passivated by AlOx nanofilms as a new means to enhance the electrical quality of graphene for its scalable utilization. Our experiments and electrical measurements on large-scale chemical vapor-deposited (CVD) graphene devices reveal that high-current treatment causes persistent and irreversible de-trapping density in both bare graphene and graphene covered by AlOx. Strikingly, despite possible interfacial defects in graphene covered with AlOx, the high-current treatment enhances its carrier mobility by up to 200% in contrast to bare graphene samples, where mobility decreases. Spatially resolved Raman spectroscopy mapping confirms that surface passivation by AlOx, followed by the current treatment, reduces the number of sp3 defects in graphene. These results suggest that for current treated-passivated graphene (CTPG), the high-current treatment considerably reduces charged impurity and trapped charge densities, thereby reducing Coulomb scattering while mitigating any electromigration of carbon atoms. Our study unveils CTPG as an innovative system for practical utilization in graphene nanoelectronic and spintronic integrated circuits.
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Affiliation(s)
- Daria Belotcerkovtceva
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala SE-751 20, Sweden.
| | - Henry Nameirakpam
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala SE-751 20, Sweden.
| | - Gopal Datt
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala SE-751 20, Sweden.
| | - Ulrich Noumbe
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala SE-751 20, Sweden.
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, 23 rue du Loess, Strasbourg 67034, France
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala SE-751 20, Sweden.
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4
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Kumari P, Rani S, Kar S, Kamalakar MV, Ray SJ. Strain-controlled spin transport in a two-dimensional (2D) nanomagnet. Sci Rep 2023; 13:16599. [PMID: 37789039 PMCID: PMC10547692 DOI: 10.1038/s41598-023-43025-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 09/18/2023] [Indexed: 10/05/2023] Open
Abstract
Semiconductors with controllable electronic transport coupled with magnetic behaviour, offering programmable spin arrangements present enticing potential for next generation intelligent technologies. Integrating and linking these two properties has been a long standing challenge for material researchers. Recent discoveries in two-dimensional (2D) magnet shows an ability to tune and control the electronic and magnetic phases at ambient temperature. Here, we illustrate controlled spin transport within the magnetic phase of the 2D semiconductor CrOBr and reveal a substantial connection between its magnetic order and charge carriers. First, we systematically analyse the strain-induced electronic behaviour of 2D CrOBr using density functional theory calculations. Our study demonstrates the phase transition from a magnetic semiconductor → half metal → magnetic metal in the material under strain application, creating intriguing spin-resolved conductance with 100% spin polarisation and spin-injection efficiency. Additionally, the spin-polarised current-voltage (I-V) trend displayed conductance variations with high strain-assisted tunability and a peak-to-valley ratio as well as switching efficiency. Our study reveals that CrOBr can exhibit highly anisotropic behaviour with perfect spin filtering, offering new implications for strain engineered magneto-electronic devices.
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Affiliation(s)
- P Kumari
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - S Rani
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - S Kar
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - S J Ray
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India.
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5
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Kar S, Kumari P, Kamalakar MV, Ray SJ. Twist-assisted optoelectronic phase control in two-dimensional (2D) Janus heterostructures. Sci Rep 2023; 13:13696. [PMID: 37608024 PMCID: PMC10444812 DOI: 10.1038/s41598-023-39993-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/03/2023] [Indexed: 08/24/2023] Open
Abstract
Atomically thin two-dimensional (2D) Janus materials and their Van der Waals heterostructures (vdWHs) have emerged as a new class of intriguing semiconductor materials due to their versatile application in electronic and optoelectronic devices. Herein, We have invstigated most probable arrangements of different inhomogeneous heterostructures employing one layer of transition metal dichalcogenide, TMD (MoS2, WS2, MoSe2, and WSe2) piled on the top of Janus TMD (MoSeTe or WSeTe) and investigated their structural, electronic as well as optical properties through first-principles based calculations. After that, we applied twist engineering between the monolayers from 0[Formula: see text] 60[Formula: see text] twist angle, which delivers lattice reconstruction and improves the performance of the vdWHs due to interlayer coupling. The result reveals that all the proposed vdWHs are dynamically and thermodynamically stable. Some vdWHs such as MoS2/MoSeTe, WS2/WSeTe, MoS2/WSeTe, MoSe2/MoSeTe, and WS2/MoSeTe exhibit direct bandgap with type-II band alignment at some specific twist angle, which shows potential for future photovoltaic devices. Moreover, the electronic property and carrier mobility can be effectively tuned in the vdWHs compared to the respective monolayers. Furthermore, the visible optical absorption of all the Janus vdWHs at [Formula: see text] = 0[Formula: see text] can be significantly enhanced due to the weak inter-layer coupling and redistribution of the charges. Therefore, the interlayer twisting not only provides an opportunity to observe new exciting properties but also gives a novel route to modulate the electronic and optoelectronic properties of the heterostructure for practical applications.
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Affiliation(s)
- S Kar
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - P Kumari
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - S J Ray
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801103, India.
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6
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Belotcerkovtceva D, Maciel RP, Berggren E, Maddu R, Sarkar T, Kvashnin YO, Thonig D, Lindblad A, Eriksson O, Kamalakar MV. Insights and Implications of Intricate Surface Charge Transfer and sp 3-Defects in Graphene/Metal Oxide Interfaces. ACS Appl Mater Interfaces 2022; 14:36209-36216. [PMID: 35867345 PMCID: PMC9376919 DOI: 10.1021/acsami.2c06626] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/29/2022] [Indexed: 06/15/2023]
Abstract
Adherence of metal oxides to graphene is of fundamental significance to graphene nanoelectronic and spintronic interfaces. Titanium oxide and aluminum oxide are two widely used tunnel barriers in such devices, which offer optimum interface resistance and distinct interface conditions that govern transport parameters and device performance. Here, we reveal a fundamental difference in how these metal oxides interface with graphene through electrical transport measurements and Raman and photoelectron spectroscopies, combined with ab initio electronic structure calculations of such interfaces. While both oxide layers cause surface charge transfer induced p-type doping in graphene, in sharp contrast to TiOx, the AlOx/graphene interface shows the presence of appreciable sp3 defects. Electronic structure calculations disclose that significant p-type doping occurs due to a combination of sp3 bonds formed between C and O atoms at the interface and possible slightly off-stoichiometric defects of the aluminum oxide layer. Furthermore, the sp3 hybridization at the AlOx/graphene interface leads to distinct magnetic moments of unsaturated bonds, which not only explicates the widely observed low spin-lifetimes in AlOx barrier graphene spintronic devices but also suggests possibilities for new hybrid resistive switching and spin valves.
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Affiliation(s)
- Daria Belotcerkovtceva
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Renan P. Maciel
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Elin Berggren
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Ramu Maddu
- Department
of Materials Science and Engineering, Uppsala
University, P.O. Box 35, SE-751 03 Uppsala, Sweden
| | - Tapati Sarkar
- Department
of Materials Science and Engineering, Uppsala
University, P.O. Box 35, SE-751 03 Uppsala, Sweden
| | - Yaroslav O. Kvashnin
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Danny Thonig
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
- School
of Science and Technology, Örebro
University, Fakultetsgatan
1, SE-70182 Örebro, Sweden
| | - Andreas Lindblad
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Olle Eriksson
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
- School
of Science and Technology, Örebro
University, Fakultetsgatan
1, SE-70182 Örebro, Sweden
| | - M. Venkata Kamalakar
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
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7
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Muscas G, Jönsson PE, Kamalakar MV. Reply to the 'Comment on "Ultralow magnetostrictive flexible ferromagnetic nanowires"' by D. Faurie, N. Challab, M. Haboussi, and F. Zighem, Nanoscale, 2022, 14, DOI: 10.1039/D1NR01773J. Nanoscale 2022; 14:1017-1018. [PMID: 35014652 PMCID: PMC8772894 DOI: 10.1039/d1nr05893b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
In the comment to our paper, D. Faurie et al. have carried out simulations on Co-nanowires subjected to tensile stress perpendicular to the length of the nanowires. According to their simulation, the low effective magnetostriction constant of the Co nanowires results from a very low transfer of stress. They suggest that a higher transfer of stress would be obtained if the wires are bent along the length of the nanowires. Here we compare the result of magneto-optical experiments conducted by bending the nanowires both along and perpendicular to their long axis. The obtained effective magnetostriction of the Co-nanowires is, within the experimental resolution, independent of the bending direction.
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Affiliation(s)
- Giuseppe Muscas
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
- Department of Physics, University of Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 Km 0.700, I-09042 Monserrato, CA, Italy.
| | - Petra E Jönsson
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
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8
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Salvador-Porroche A, Sangiao S, Magén C, Barrado M, Philipp P, Belotcerkovtceva D, Kamalakar MV, Cea P, De Teresa JM. Highly-efficient growth of cobalt nanostructures using focused ion beam induced deposition under cryogenic conditions: application to electrical contacts on graphene, magnetism and hard masking. Nanoscale Adv 2021; 3:5656-5662. [PMID: 36133267 PMCID: PMC9418482 DOI: 10.1039/d1na00580d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 08/20/2021] [Indexed: 05/28/2023]
Abstract
Emergent technologies are required in the field of nanoelectronics for improved contacts and interconnects at nano and micro-scale. In this work, we report a highly-efficient nanolithography process for the growth of cobalt nanostructures requiring an ultra-low charge dose (15 μC cm-2, unprecedented in single-step charge-based nanopatterning). This resist-free process consists in the condensation of a ∼28 nm-thick Co2(CO)8 layer on a substrate held at -100 °C, its irradiation with a Ga+ focused ion beam, and substrate heating up to room temperature. The resulting cobalt-based deposits exhibit sub-100 nm lateral resolution, display metallic behaviour (room-temperature resistivity of 200 μΩ cm), present ferromagnetic properties (magnetization at room temperature of 400 emu cm-3) and can be grown in large areas. To put these results in perspective, similar properties can be achieved by room-temperature focused ion beam induced deposition and the same precursor only if a 2 × 103 times higher charge dose is used. We demonstrate the application of such an ultra-fast growth process to directly create electrical contacts onto graphene ribbons, opening the route for a broad application of this technology to any 2D material. In addition, the application of these cryo-deposits for hard masking is demonstrated, confirming its structural functionality.
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Affiliation(s)
- Alba Salvador-Porroche
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza 50009 Zaragoza Spain
| | - Soraya Sangiao
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza 50009 Zaragoza Spain
- Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza 50018 Zaragoza Spain
| | - César Magén
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza 50009 Zaragoza Spain
- Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza 50018 Zaragoza Spain
| | - Mariano Barrado
- Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza 50018 Zaragoza Spain
| | - Patrick Philipp
- Advanced Instrumentation for Nano-Analytics (AINA), MRT Department, Luxembourg Institute of Science and Technology (LIST) 41 rue du Brill 4422 Belvaux Luxembourg
| | - Daria Belotcerkovtceva
- Department of Physics and Astronomy, Uppsala University Box 516 SE-751 20 Uppsala Sweden
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University Box 516 SE-751 20 Uppsala Sweden
| | - Pilar Cea
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza 50009 Zaragoza Spain
- Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza 50018 Zaragoza Spain
| | - José María De Teresa
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza 50009 Zaragoza Spain
- Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza 50018 Zaragoza Spain
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9
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Datt G, Kotnana G, Maddu R, Vallin Ö, Joshi DC, Peddis D, Barucca G, Kamalakar MV, Sarkar T. Combined Bottom-Up and Top-Down Approach for Highly Ordered One-Dimensional Composite Nanostructures for Spin Insulatronics. ACS Appl Mater Interfaces 2021; 13:37500-37509. [PMID: 34325507 PMCID: PMC8397244 DOI: 10.1021/acsami.1c09582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 07/19/2021] [Indexed: 06/13/2023]
Abstract
Engineering magnetic proximity effects-based devices requires developing efficient magnetic insulators. In particular, insulators, where magnetic phases show dramatic changes in texture on the nanometric level, could allow us to tune the proximity-induced exchange splitting at such distances. In this paper, we report the fabrication and characterization of highly ordered two-dimensional arrays of LaFeO3 (LFO)-CoFe2O4 (CFO) biphasic magnetic nanowires, grown on silicon substrates using a unique combination of bottom-up and top-down synthesis approaches. The regularity of the patterns was confirmed using atomic force microscopy and scanning electron microscopy techniques, whereas magnetic force microscopy images established the magnetic homogeneity of the patterned nanowires and absence of any magnetic debris between the wires. Transmission electron microscopy shows a close spatial correlation between the LFO and CFO phases, indicating strong grain-to-grain interfacial coupling, intrinsically different from the usual core-shell structures. Magnetic hysteresis loops reveal the ferrimagnetic nature of the composites up to room temperature and the presence of a strong magnetic coupling between the two phases, and electrical transport measurements demonstrate the strong insulating behavior of the LFO-CFO composite, which is found to be governed by Mott-variable range hopping conduction mechanisms. A shift in the Raman modes in the composite sample compared to those of pure CFO suggests the existence of strain-mediated elastic coupling between the two phases in the composite sample. Our work offers ordered composite nanowires with strong interfacial coupling between the two phases that can be directly integrated for developing multiphase spin insulatronic devices and emergent magnetic interfaces.
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Affiliation(s)
- Gopal Datt
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
| | - Ganesh Kotnana
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
| | - Ramu Maddu
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
| | - Örjan Vallin
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
| | - Deep Chandra Joshi
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
| | - Davide Peddis
- Dipartimento
di Chimica e Chimica Industriale, Università
di Genova, Via Dodecaneso
31, Genova I-16146, Italy
- Institute
of Structure of Matter, Italian National
Research Council (CNR), Monterotondo
Scalo, 00015 Rome, Italy
| | - Gianni Barucca
- Department
SIMAU, Università Politecnica delle
Marche, Via Brecce Bianche
12, Ancona 60131, Italy
| | - M. Venkata Kamalakar
- Department
of Physics and Astronomy, Uppsala University, Uppsala SE-751 20, Sweden
| | - Tapati Sarkar
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, Uppsala SE-751
03, Sweden
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10
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Muscas G, Jönsson PE, Serrano IG, Vallin Ö, Kamalakar MV. Ultralow magnetostrictive flexible ferromagnetic nanowires. Nanoscale 2021; 13:6043-6052. [PMID: 33885602 DOI: 10.1039/d0nr08355k] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The integration of magneto-electric and spintronic sensors to flexible electronics presents a huge potential for advancing flexible and wearable technologies. Magnetic nanowires are core components for building such devices. Therefore, realizing flexible magnetic nanowires with engineered magneto-elastic properties is key to flexible spintronic circuits, as well as creating unique pathways to explore complex flexible spintronic, magnonic, and magneto-plasmonic devices. Here, we demonstrate highly resilient flexible ferromagnetic nanowires on transparent flexible substrates for the first time. Through extensive magneto-optical Kerr experiments, exploring the Villari effect, we reveal an ultralow magnetostrictive constant in nanowires, a two-order reduced value compared to bulk values. In addition, the flexible magnetic nanowires exhibit remarkable resilience sustaining bending radii ∼5 mm, high endurance, and enhanced elastic limit compared to thin films of similar thickness and composition. The observed performance is corroborated by our micro-magnetic simulations and can be attributed to the reduced size and strong nanostructure-interfacial effects. Such stable magnetic nanowires with ultralow magnetostriction open up new opportunities for stable surface mountable and wearable spintronic sensors, advanced nanospintronic circuits, and for exploring novel strain-induced quantum effects in hybrid devices.
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Affiliation(s)
- Giuseppe Muscas
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
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11
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Panda J, Ramu M, Karis O, Sarkar T, Kamalakar MV. Ultimate Spin Currents in Commercial Chemical Vapor Deposited Graphene. ACS Nano 2020; 14:12771-12780. [PMID: 32945650 PMCID: PMC7596785 DOI: 10.1021/acsnano.0c03376] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 09/18/2020] [Indexed: 06/01/2023]
Abstract
Establishing ultimate spin current efficiency in graphene over industry-standard substrates can facilitate research and development exploration of spin current functions and spin sensing. At the same time, it can resolve core issues in spin relaxation physics while addressing the skepticism of graphene's practicality for planar spintronic applications. In this work, we reveal an exceptionally long spin communication capability of 45 μm and highest to date spin diffusion length of 13.6 μm in graphene on SiO2/Si at room temperature. Employing commercial chemical vapor deposited (CVD) graphene, we show how contact-induced surface charge transfer doping and device doping contributions, as well as spin relaxation, can be quenched in extremely long spin channels and thereby enable unexpectedly long spin diffusion lengths in polycrystalline CVD graphene. Extensive experiments show enhanced spin transport and precession in multiple longest channels (36 and 45 μm) that reveal the highest spin lifetime of ∼2.5-3.5 ns in graphene over SiO2/Si, even under ambient conditions. Such performance, made possible due to our devices approaching the intrinsic spin-orbit coupling of ∼20 μeV in graphene, reveals the role of the D'yakonov-Perel' spin relaxation mechanism in graphene channels as well as contact regions. Our record demonstration, fresh device engineering, and spin relaxation insights unlock the ultimate spin current capabilities of graphene on SiO2/Si, while the robust high performance of commercial CVD graphene can proliferate research and development of innovative spin sensors and spin computing circuits.
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Affiliation(s)
- J. Panda
- Department
of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - M. Ramu
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, SE-751 03 Uppsala, Sweden
| | - Olof Karis
- Department
of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Tapati Sarkar
- Department
of Materials Science and Engineering, Uppsala
University, Box 35, SE-751 03 Uppsala, Sweden
| | - M. Venkata Kamalakar
- Department
of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
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12
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Serrano IG, Panda J, Edvinsson T, Kamalakar MV. Flexible transparent graphene laminates via direct lamination of graphene onto polyethylene naphthalate substrates. Nanoscale Adv 2020; 2:3156-3163. [PMID: 36134291 PMCID: PMC9416925 DOI: 10.1039/d0na00046a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 06/08/2020] [Indexed: 05/31/2023]
Abstract
Graphene, with its excellent electrical, mechanical, and optical properties, has emerged as an exceptional material for flexible and transparent nanoelectronics. Such versatility makes it compelling to find new pathways to lay graphene sheets onto smooth, flexible substrates to create large-scale flexible transparent graphene conductors. Here, we report the realization of flexible transparent graphene laminates by direct adhesion of chemical vapor deposition (CVD) graphene on a polyethylene naphthalate (PEN) substrate, which is an emerging standard for flexible electronics. By systematically optimizing the conditions of a hot-press technique, we have identified that applying optimum temperature and pressure can make graphene directly adhere to flexible PEN substrates without any intermediate layer. The resultant flexible graphene films are transparent, have a standard sheet resistance of 1 kΩ with high bending resilience, and high optical transmittance of 85%. Our direct hot-press method is achieved below the glass transition temperature of the PEN substrate. Furthermore, we demonstrate press-assisted embossing for patterned transfer of graphene, and hence it can serve as a reliable new means for creating universal, transparent conducting patterned films for designing flexible nanoelectronic and optoelectronic components.
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Affiliation(s)
- Ismael G Serrano
- Department of Physics and Astronomy, Uppsala University Box 516 SE-751 20 Uppsala Sweden
| | - J Panda
- Department of Physics and Astronomy, Uppsala University Box 516 SE-751 20 Uppsala Sweden
| | - Tomas Edvinsson
- Department of Materials Science and Engineering, Uppsala University Box 534 SE-751 21 Uppsala Sweden
| | - M Venkata Kamalakar
- Department of Physics and Astronomy, Uppsala University Box 516 SE-751 20 Uppsala Sweden
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13
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Nair AK, Rani S, Kamalakar MV, Ray SJ. Bi-stimuli assisted engineering and control of magnetic phase in monolayer CrOCl. Phys Chem Chem Phys 2020; 22:12806-12813. [PMID: 32469019 DOI: 10.1039/d0cp01204a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Magnetic phase control and room temperature magnetic stability in two-dimensional (2D) materials are indispensable for realising advanced spintronic and magneto-electronic functions. Our current work employs first-principles calculations to comprehensively study the magnetic behaviour of 2D CrOCl, uncovering the impact of strain and electric field on the material. Our studies have revealed that uniaxial strain leads to the feasibility of room temperature ferromagnetism in the layer and also detected the occurrence of a ferromagnetic → antiferromagnetic phase transition in the system, which is anisotropic along the armchair and zigzag directions. Beyond such a strain effect, the coupling of strain and electric field leads to a remarkable enhancement of the Curie temperature (Tc) ∼ 450 K in CrOCl. These predictions based on our detailed simulations show the prospect of multi-stimuli magnetic phase control, which could have great significance for realizing magneto-mechanical sensors.
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Affiliation(s)
- A K Nair
- Department of Physics, Indian Institute of Technology Patna, Bihta 801106, India.
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14
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Abstract
Recent reports on the two-dimensional (2D) material CrOCl revealed magnetic ordering and spin polarisation with Curie Temperature T c ∼ 160 K, values higher than most diluted magnetic semiconductors. Here, we investigate the uniaxial and biaxial strain-dependent electronic and transport properties of CrOCl monolayer using first-principles based calculations. The calculated Young's modulus indicates high mechanical flexibility for the application of high strain. Our study shows that strain can induce phase changes from a bipolar magnetic semiconductor → half metal → magnetic metal in the material, leading to interesting spin-resolved conductance with 100% spin filtering. Furthermore, the current-voltage (I-V) response showed conductance fluctuations, characterised by peak to valley ratio and switching efficiency offering high strain assisted tunability. Overall, CrOCl shows a highly anisotropic behaviour with the material displaying 100% spin polarisation in the tensile strain region. The electronic, transport and mechanical properties indicate that CrOCl is a versatile 2D material with multi-phase capabilities having promising applications for future nanospintronic devices.
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Affiliation(s)
- S Rani
- Department of Physics, Indian Institute of Technology Patna, Bihta 801106, India
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15
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Kumari P, Majumder S, Rani S, Nair AK, Kumari K, Kamalakar MV, Ray SJ. High efficiency spin filtering in magnetic phosphorene. Phys Chem Chem Phys 2020; 22:5893-5901. [DOI: 10.1039/c9cp05390e] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We present high efficiency spin filtering behaviour in magnetically rendered phosphorene, doped with various 3d block elements. A phase diagram was obtained depicting the presence of various electronic and magnetic states.
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Affiliation(s)
- P. Kumari
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | - S. Majumder
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | - S. Rani
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | - A. K. Nair
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | - K. Kumari
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | | | - S. J. Ray
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
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16
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Abstract
Owing to their unprecedented electronic properties, graphene and two-dimensional (2D) crystals have brought fresh opportunities for advances in planar spintronic devices. Graphene is an ideal medium for spin transport while being an exceptionally resilient material for flexible nanoelectronics. However, these extraordinary traits have never been combined to create flexible graphene spin circuits. Realizing such circuits could lead to bendable strain-spin sensors, as well as a unique platform to explore pure spin current based operations and low-power 2D flexible nanoelectronics. Here, we demonstrate graphene spin circuits on flexible substrates for the first time. Despite the rough topography of the flexible substrates, these circuits prepared with chemical vapor deposited monolayer graphene reveal an efficient room temperature spin transport with distinctively large spin diffusion coefficients ∼0.2 m2 s-1. Compared to earlier graphene devices on Si/SiO2 substrates, such values are up to 20 times larger, leading to one order higher spin signals and an enhanced spin diffusion length ∼10 μm in graphene-based nonlocal spin valves fabricated using industry standard systems. This high performance arising out of a characteristic substrate terrain shows promise of a scalable and flexible platform towards flexible 2D spintronics. Our innovation is a key step for the exploration of strain-dependent 2D spin phenomena and paves the way for flexible graphene spin memory-logic units and planar spin sensors.
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Affiliation(s)
- I G Serrano
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
| | - J Panda
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
| | - Fernand Denoel
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
| | - Örjan Vallin
- Department of Engineering Sciences , Uppsala University , Box 534, SE 751 21 , Uppsala , Sweden
| | - Dibya Phuyal
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
| | - Olof Karis
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
| | - M Venkata Kamalakar
- Department of Physics and Astronomy , Uppsala University , Box 516, SE 751 20 , Uppsala , Sweden
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17
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Abstract
Phosphorene is a unique two-dimensional semiconductor that has huge potential for nanoelectronic and spintronic applications. In the presence of various 3d block elements, remarkable feasibility of ferromagnetism and antiferromagnetism up to a large temperature ∼1150 K was observed.
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Affiliation(s)
- A. K. Nair
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | - P. Kumari
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
| | | | - S. J. Ray
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
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18
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Abstract
We investigated the strain phase diagram of phosphorene and observed strain-tuneable conductance oscillations that are robust against doping and defects.
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Affiliation(s)
- S. J. Ray
- Department of Physics
- Indian Institute of Technology Patna
- Bihta 801106
- India
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19
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Dankert A, Pashaei P, Kamalakar MV, Gaur APS, Sahoo S, Rungger I, Narayan A, Dolui K, Hoque MA, Patel RS, de Jong MP, Katiyar RS, Sanvito S, Dash SP. Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide. ACS Nano 2017; 11:6389-6395. [PMID: 28557439 DOI: 10.1021/acsnano.7b02819] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.
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Affiliation(s)
- André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-41296, Göteborg, Sweden
| | - Parham Pashaei
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-41296, Göteborg, Sweden
| | - M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-41296, Göteborg, Sweden
- Department of Physics and Astronomy, Uppsala University , Box 516, 75120, Uppsala, Sweden
| | - Anand P S Gaur
- Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico , San Juan, PR 00931, United States
- Mechanical Engineering Department, Iowa State University , Ames, Iowa 50011, United States
| | - Satyaprakash Sahoo
- Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico , San Juan, PR 00931, United States
- Institute of Physics , Bhubaneswar, Odisha 751005, India
| | - Ivan Rungger
- National Physical Laboratory , Teddington, TW11 0LW, United Kingdom
| | - Awadhesh Narayan
- School of Physics, AMBER and CRANN Institute, Trinity College , Dublin 2, Ireland
- Materials Theory, ETH Zurich , Wolfgang-Pauli-Strasse 27, CH 8093, Zurich, Switzerland
| | - Kapildeb Dolui
- School of Physics, AMBER and CRANN Institute, Trinity College , Dublin 2, Ireland
- Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716-2570, United States
| | - Md Anamul Hoque
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-41296, Göteborg, Sweden
| | - Ram Shanker Patel
- Department of Physics, Birla Institute of Technology and Science , Pilani - K K Birla Goa Campus, Zuarinagar, 403726, Goa, India
| | - Michel P de Jong
- MESA+ Institute for Nanotechnology University of Twente , 7500 AE Enschede, The Netherlands
| | - Ram S Katiyar
- Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico , San Juan, PR 00931, United States
| | - Stefano Sanvito
- School of Physics, AMBER and CRANN Institute, Trinity College , Dublin 2, Ireland
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE-41296, Göteborg, Sweden
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20
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Abstract
Phosphorene is a newly unveiled two-dimensional crystal with immense potential for nanoelectronic and optoelectronic applications. Its unique electronic structure and two dimensionality also present opportunities for single electron devices. Here we report the behaviour of a single electron transistor (SET) made of a phosphorene island, explored for the first time using ab initio calculations. We find that the band gap and the charging energy decrease monotonically with increasing layer numbers due to weak quantum confinement. When compared to two other novel 2D crystals such as graphene and MoS2, our investigation reveals larger adsorption energies of gas molecules on phosphorene, which indicates better a sensing ability. The calculated charge stability diagrams show distinct changes in the presence of an individual molecule which can be applied to detect the presence of different molecules with sensitivity at a single molecular level. The higher charging energies of the molecules within the SET display operational viability at room temperature, which is promising for possible ultra sensitive detection applications.
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Affiliation(s)
- S J Ray
- Department of Physics, Indian Institute of Technology Patna, Bitha, 801 103, Bihar, India
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21
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Kamalakar MV, Dankert A, Kelly PJ, Dash SP. Inversion of Spin Signal and Spin Filtering in Ferromagnet|Hexagonal Boron Nitride-Graphene van der Waals Heterostructures. Sci Rep 2016; 6:21168. [PMID: 26883717 PMCID: PMC4756790 DOI: 10.1038/srep21168] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 01/12/2016] [Indexed: 12/04/2022] Open
Abstract
Two dimensional atomically thin crystals of graphene and its insulating isomorph hexagonal boron nitride (h-BN) are promising materials for spintronic applications. While graphene is an ideal medium for long distance spin transport, h-BN is an insulating tunnel barrier that has potential for efficient spin polarized tunneling from ferromagnets. Here, we demonstrate the spin filtering effect in cobalt|few layer h-BN|graphene junctions leading to a large negative spin polarization in graphene at room temperature. Through nonlocal pure spin transport and Hanle precession measurements performed on devices with different interface barrier conditions, we associate the negative spin polarization with high resistance few layer h-BN|ferromagnet contacts. Detailed bias and gate dependent measurements reinforce the robustness of the effect in our devices. These spintronic effects in two-dimensional van der Waals heterostructures hold promise for future spin based logic and memory applications.
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Affiliation(s)
- M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden.,Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Paul J Kelly
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
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22
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Dankert A, Geurs J, Kamalakar MV, Charpentier S, Dash SP. Room Temperature Electrical Detection of Spin Polarized Currents in Topological Insulators. Nano Lett 2015; 15:7976-7981. [PMID: 26560203 DOI: 10.1021/acs.nanolett.5b03080] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Topological insulators (TIs) are a new class of quantum materials that exhibit a current-induced spin polarization due to spin-momentum locking of massless Dirac Fermions in their surface states. This helical spin polarization in three-dimensional (3D) TIs has been observed using photoemission spectroscopy up to room temperatures. Recently, spin polarized surface currents in 3D TIs were detected electrically by potentiometric measurements using ferromagnetic detector contacts. However, these electric measurements are so far limited to cryogenic temperatures. Here we report the room temperature electrical detection of the spin polarization on the surface of Bi2Se3 by employing spin sensitive ferromagnetic tunnel contacts. The current-induced spin polarization on the Bi2Se3 surface is probed by measuring the magnetoresistance while switching the magnetization direction of the ferromagnetic detector. A spin resistance of up to 70 mΩ is measured at room temperature, which increases linearly with current bias, reverses sign with current direction, and decreases with higher TI thickness. The magnitude of the spin signal, its sign, and control experiments, using different measurement geometries and interface conditions, rule out other known physical effects. These findings provide further information about the electrical detection of current-induced spin polarizations in 3D TIs at ambient temperatures and could lead to innovative spin-based technologies.
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Affiliation(s)
- André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Johannes Geurs
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Sophie Charpentier
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
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23
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Kamalakar MV, Madhushankar BN, Dankert A, Dash SP. Low Schottky barrier black phosphorus field-effect devices with ferromagnetic tunnel contacts. Small 2015; 11:2209-2216. [PMID: 25586013 DOI: 10.1002/smll.201402900] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 11/12/2014] [Indexed: 06/04/2023]
Abstract
Black phosphorus (BP) has been recently unveiled as a promising 2D direct bandgap semiconducting material. Here, ambipolar field-effect transistor behavior of nanolayers of BP with ferromagnetic tunnel contacts is reported. Using TiO2/Co contacts, a reduced Schottky barrier <50 meV, which can be tuned further by the gate voltage, is obtained. Eminently, a good transistor performance is achieved in the devices discussed here, with drain current modulation of four to six orders of magnitude and a mobility of μh ≈ 155 cm(2) V(-1) s(-1) for hole conduction at room temperature. Magnetoresistance calculations using a spin diffusion model reveal that the source-drain contact resistances in the BP device can be tuned by gate voltage to an optimal range for injection and detection of spin-polarized holes. The results of the study demonstrate the prospect of BP nanolayers for efficient nanoelectronic and spintronic devices.
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Affiliation(s)
- M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
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24
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Devid EJ, Martinho PN, Kamalakar MV, Šalitroš I, Prendergast Ú, Dayen JF, Meded V, Lemma T, González-Prieto R, Evers F, Keyes TE, Ruben M, Doudin B, van der Molen SJ. Spin transition in arrays of gold nanoparticles and spin crossover molecules. ACS Nano 2015; 9:4496-4507. [PMID: 25835284 DOI: 10.1021/acsnano.5b01103] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate if the functionality of spin crossover molecules is preserved when they are assembled into an interfacial device structure. Specifically, we prepare and investigate gold nanoparticle arrays, into which room-temperature spin crossover molecules are introduced, more precisely, [Fe(AcS-BPP)2](ClO4)2, where AcS-BPP = (S)-(4-{[2,6-(dipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)ethanethioate (in short, Fe(S-BPP)2). We combine three complementary experiments to characterize the molecule-nanoparticle structure in detail. Temperature-dependent Raman measurements provide direct evidence for a (partial) spin transition in the Fe(S-BPP)2-based arrays. This transition is qualitatively confirmed by magnetization measurements. Finally, charge transport measurements on the Fe(S-BPP)2-gold nanoparticle devices reveal a minimum in device resistance versus temperature, R(T), curves around 260-290 K. This is in contrast to similar networks containing passive molecules only that show monotonically decreasing R(T) characteristics. Backed by density functional theory calculations on single molecular conductance values for both spin states, we propose to relate the resistance minimum in R(T) to a spin transition under the hypothesis that (1) the molecular resistance of the high spin state is larger than that of the low spin state and (2) transport in the array is governed by a percolation model.
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Affiliation(s)
- Edwin J Devid
- †Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Paulo N Martinho
- ‡Centro de Química e Bioquímica (CQB), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - M Venkata Kamalakar
- §Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden
| | - Ivan Šalitroš
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- ◊Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinskeho 9, SK-812 37, Bratislava, Slovakia
| | - Úna Prendergast
- ⊥School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Jean-François Dayen
- #Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS UMR 7504, Laboratory NIE, Université de Strasbourg, 23 Rue du Loess, 67034 Strasbourg, France
| | - Velimir Meded
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Tibebe Lemma
- ⊥School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Rodrigo González-Prieto
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- ¶Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Ferdinand Evers
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- △Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1, D-76128 Karlsruhe, Germany
| | - Tia E Keyes
- ⊥School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Mario Ruben
- ∥Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- #Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS UMR 7504, Laboratory NIE, Université de Strasbourg, 23 Rue du Loess, 67034 Strasbourg, France
| | - Bernard Doudin
- #Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS UMR 7504, Laboratory NIE, Université de Strasbourg, 23 Rue du Loess, 67034 Strasbourg, France
| | - Sense Jan van der Molen
- †Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University P.O. Box 9504, 2300 RA Leiden, The Netherlands
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25
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Kamalakar MV, Groenveld C, Dankert A, Dash SP. Long distance spin communication in chemical vapour deposited graphene. Nat Commun 2015; 6:6766. [PMID: 25857650 PMCID: PMC4433146 DOI: 10.1038/ncomms7766] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 02/24/2015] [Indexed: 12/21/2022] Open
Abstract
Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ∼6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications.
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Affiliation(s)
- M. Venkata Kamalakar
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Kemivagen 9, SE-41296 Göteborg, Sweden
| | - Christiaan Groenveld
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Kemivagen 9, SE-41296 Göteborg, Sweden
| | - André Dankert
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Kemivagen 9, SE-41296 Göteborg, Sweden
| | - Saroj P. Dash
- Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Kemivagen 9, SE-41296 Göteborg, Sweden
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Devid EJ, Martinho PN, Kamalakar MV, Prendergast Ú, Kübel C, Lemma T, Dayen JF, Keyes TE, Doudin B, Ruben M, van der Molen SJ. The influence of molecular mobility on the properties of networks of gold nanoparticles and organic ligands. Beilstein J Nanotechnol 2014; 5:1664-1674. [PMID: 25383278 PMCID: PMC4222375 DOI: 10.3762/bjnano.5.177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 08/26/2014] [Indexed: 06/04/2023]
Abstract
We prepare and investigate two-dimensional (2D) single-layer arrays and multilayered networks of gold nanoparticles derivatized with conjugated hetero-aromatic molecules, i.e., S-(4-{[2,6-bipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)thiolate (herein S-BPP), as capping ligands. These structures are fabricated by a combination of self-assembly and microcontact printing techniques, and are characterized by electron microscopy, UV-visible spectroscopy and Raman spectroscopy. Selective binding of the S-BPP molecules to the gold nanoparticles through Au-S bonds is found, with no evidence for the formation of N-Au bonds between the pyridine or pyrazole groups of BPP and the gold surface. Subtle, but significant shifts with temperature of specific Raman S-BPP modes are also observed. We attribute these to dynamic changes in the orientation and/or increased mobility of the molecules on the gold nanoparticle facets. As for their conductance, the temperature-dependence for S-BPP networks differs significantly from standard alkanethiol-capped networks, especially above 220 K. Relating the latter two observations, we propose that dynamic changes in the molecular layers effectively lower the molecular tunnel barrier for BPP-based arrays at higher temperatures.
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Affiliation(s)
- Edwin J Devid
- Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - Paulo N Martinho
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Centro de Química e Bioquímica (CQB), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
| | - M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden
| | - Úna Prendergast
- School of Chemical Science, Dublin City University (DCU), Dublin 9, Ireland
| | - Christian Kübel
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Karlsruhe Nano Micro Facility (KNMF) Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Tibebe Lemma
- School of Chemical Science, Dublin City University (DCU), Dublin 9, Ireland
| | - Jean-François Dayen
- Université de Strasbourg, IPCMS-CMRS UMR 7504, 23 Rue du Loess, 67034 Strasbourg, France
| | - Tia E Keyes
- School of Chemical Science, Dublin City University (DCU), Dublin 9, Ireland
| | - Bernard Doudin
- Université de Strasbourg, IPCMS-CMRS UMR 7504, 23 Rue du Loess, 67034 Strasbourg, France
| | - Mario Ruben
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Université de Strasbourg, IPCMS-CMRS UMR 7504, 23 Rue du Loess, 67034 Strasbourg, France
| | - Sense Jan van der Molen
- Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
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Kamalakar MV, Dankert A, Bergsten J, Ive T, Dash SP. Enhanced tunnel spin injection into graphene using chemical vapor deposited hexagonal boron nitride. Sci Rep 2014; 4:6146. [PMID: 25156685 PMCID: PMC4143790 DOI: 10.1038/srep06146] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 07/31/2014] [Indexed: 12/22/2022] Open
Abstract
The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene.
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Affiliation(s)
- M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Johan Bergsten
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Tommy Ive
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
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Raychaudhuri AK, Kamalakar MV. Electrical measurements on single nanowires and nanotubes of metals and its correlation with structural characterization. J Anal Sci Technol 2011. [DOI: 10.5355/jast.2011.a66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Abstract
In this paper we report the first experimental study of critical phenomena in case of magnetic nanowires of nickel near the ferromagnetic-paramagnetic transition from the electrical transport properties. Nickel nanowire arrays, prepared by potentiostatic electrodeposition of nickel inside pores of nanoporous anodic alumina template were well characterized by X-ray Diffraction, Transmission electron microscopy and Energy dispersive Spectroscopy. Precise electrical resistance measurement of the nanowire arrays of wire diameter 20 nm have been done in the temperature range between 300 K to 700 K. We see a drop in the Curie temperature as observed from the resistivity anomaly. We analyzed the resistance data near the critical region and extracted the critical exponent alpha directly from the resistance. We observed a decrease in the critical part of the resistivity including a decrease in the magnitude of the critical exponent alpha and severe modification in the correction to scaling.
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Affiliation(s)
- M Venkata Kamalakar
- Department of Material Science, DST Unit for Nanosciences, S. N. Bose National Centre for Basic Sciences, Salt Lake, Sector-III, Kolkata 700098, India
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Sarkar T, Kamalakar MV, Raychaudhuri AK. Transport properties of nanoparticles of complex oxides: likely presence of Coulomb blockade at low temperature. J Nanosci Nanotechnol 2009; 9:5315-5322. [PMID: 19928221 DOI: 10.1166/jnn.2009.1140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper we report transport properties at low temperatures (3 K < or = T < or = 300 K) in nanostructured functional oxides. Electrical resistivity in the nanoparticles of La0.5CoO3 (LSCO), a ferromagnet, show a gradual change-over from a completely metallic state (in the bulk sample) to a completely insulating state (in the sample with the smallest particle size of approximately 35 nm), while still remaining a ferromagnet, albeit with a lower Tc. In the LSCO nanoparticles (diameter <60 nm) there is a change-over in the temperature dependence of the resistivity at the lowest temperature (T <10 K) which we could identify as arising from the Coulomb blockade in the conducting grains which are separated by insulating grain boundaries that allow transport by tunneling. However, nanoparticles of the nonmagnetic material, LaNiO3 (LNO) remain metallic (similar to the bulk sample) throughout the temperature range studied with the resistivity reaching a temperature independent value at the lowest temperature measured. We suggest that the essential difference between the electrical transport in these nanostructured materials arises due to the physical nature of the grain boundaries which is insulating in LSCO due to absence of long range spin order that is needed for the metallic state.
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Affiliation(s)
- Tapati Sarkar
- DST Unit for Nanosciences, Department of Material Science, S. N. Bose National Center for Basic Sciences, Salt Lake Sector-III, Kolkata 700098, India
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Samanta S, Kamalakar MV, Raychaudhuri AK. Investigation of very low-frequency noise in ferromagnetic nickel nanowires. J Nanosci Nanotechnol 2009; 9:5243-5247. [PMID: 19928207 DOI: 10.1166/jnn.2009.1146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this paper we report very low-frequency (0.1 mHz-1.0 Hz) resistance fluctuation (noise) in Nickel nanowires of diameter 20 nm in the temperature range 77 K-300 K. The wires are one-dimensional magnetic systems since the diameter is less than the domain wall width. We found a clear signature of deviation of the spectral power from 1/f noise at low frequencies showing excess fluctuations with very slow dynamics. The magnitude of resistance fluctuations increases by an order of magnitude when the diameter of the wires is reduced below the domain wall width of nickel. The excess resistance fluctuation has been linked to thermally activated magnetization reversal and the associated domain wall motion.
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Affiliation(s)
- Sudeshna Samanta
- DST Unit for Nanosciences, Department of Material Science, S. N. Bose National Center for Basic Sciences, JD Block, Sector-Ill, Salt Lake, Kolkata 700098, India
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