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Moya C, Escoda-Torroella M, Rodríguez-Álvarez J, Figueroa AI, García Í, Ferrer-Vidal IB, Gallo-Cordova A, Puerto Morales M, Aballe L, Fraile Rodríguez A, Labarta A, Batlle X. Unveiling the crystal and magnetic texture of iron oxide nanoflowers. Nanoscale 2024; 16:1942-1951. [PMID: 38170857 DOI: 10.1039/d3nr04608g] [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: 01/05/2024]
Abstract
Iron oxide nanoflowers (IONF) are densely packed multi-core aggregates known for their high saturation magnetization and initial susceptibility, as well as low remanence and coercive field. This study reports on how the local magnetic texture originating at the crystalline correlations among the cores determines the special magnetic properties of individual IONF over a wide size range from 40 to 400 nm. Regardless of this significant size variation in the aggregates, all samples exhibit a consistent crystalline correlation that extends well beyond the IONF cores. Furthermore, a nearly zero remnant magnetization, together with the presence of a persistently blocked state, and almost temperature-independent field-cooled magnetization, support the existence of a 3D magnetic texture throughout the IONF. This is confirmed by magnetic transmission X-ray microscopy images of tens of individual IONF, showing, in all cases, a nearly demagnetized state caused by the vorticity of the magnetic texture. Micromagnetic simulations agree well with these experimental findings, showing that the interplay between the inter-core direct exchange coupling and the demagnetizing field is responsible for the highly vortex-like spin configuration that stabilizes at low magnetic fields and appears to have partial topological protection. Overall, this comprehensive study provides valuable insights into the impact of crystalline texture on the magnetic properties of IONF over a wide size range, offering a deeper understanding of their potential applications in fields such as biomedicine and water remediation.
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Affiliation(s)
- Carlos Moya
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Mariona Escoda-Torroella
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Javier Rodríguez-Álvarez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Adriana I Figueroa
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Íker García
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
| | - Inés Batalla Ferrer-Vidal
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
| | - A Gallo-Cordova
- Department of Nanoscience and Nanotechnology, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - M Puerto Morales
- Department of Nanoscience and Nanotechnology, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - Lucía Aballe
- ALBA Synchrotron Light Facility, CELLS, 08290 Barcelona, Spain
| | - Arantxa Fraile Rodríguez
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Amílcar Labarta
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Xavier Batlle
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
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2
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Lv H, da Silva A, Figueroa AI, Guillemard C, Aguirre IF, Camosi L, Aballe L, Valvidares M, Valenzuela SO, Schubert J, Schmidbauer M, Herfort J, Hanke M, Trampert A, Engel-Herbert R, Ramsteiner M, Lopes JMJ. Large-Area Synthesis of Ferromagnetic Fe 5- x GeTe 2 /Graphene van der Waals Heterostructures with Curie Temperature above Room Temperature. Small 2023; 19:e2302387. [PMID: 37231567 DOI: 10.1002/smll.202302387] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/10/2023] [Indexed: 05/27/2023]
Abstract
Van der Waals (vdW) heterostructures combining layered ferromagnets and other 2D crystals are promising building blocks for the realization of ultracompact devices with integrated magnetic, electronic, and optical functionalities. Their implementation in various technologies depends strongly on the development of a bottom-up scalable synthesis approach allowing for realizing highly uniform heterostructures with well-defined interfaces between different 2D-layered materials. It is also required that each material component of the heterostructure remains functional, which ideally includes ferromagnetic order above room temperature for 2D ferromagnets. Here, it is demonstrated that the large-area growth of Fe5- x GeTe2 /graphene heterostructures is achieved by vdW epitaxy of Fe5- x GeTe2 on epitaxial graphene. Structural characterization confirms the realization of a continuous vdW heterostructure film with a sharp interface between Fe5- x GeTe2 and graphene. Magnetic and transport studies reveal that the ferromagnetic order persists well above 300 K with a perpendicular magnetic anisotropy. In addition, epitaxial graphene on SiC(0001) continues to exhibit a high electronic quality. These results represent an important advance beyond nonscalable flake exfoliation and stacking methods, thus marking a crucial step toward the implementation of ferromagnetic 2D materials in practical applications.
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Affiliation(s)
- Hua Lv
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Alessandra da Silva
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Adriana I Figueroa
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, 08193, Spain
| | - Charles Guillemard
- ALBA Synchrotron Light Source, Cerdanyola del Valles, Barcelona, 08290, Spain
| | - Iván Fernández Aguirre
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, 08193, Spain
- Universitat Autònoma de Barcelona, Bellaterra, Barcelona, 08193, Spain
| | - Lorenzo Camosi
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, 08193, Spain
| | - Lucia Aballe
- ALBA Synchrotron Light Source, Cerdanyola del Valles, Barcelona, 08290, Spain
| | - Manuel Valvidares
- ALBA Synchrotron Light Source, Cerdanyola del Valles, Barcelona, 08290, Spain
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona, 08193, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, 08010, Spain
| | - Jürgen Schubert
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, 52425, Jülich, Germany
| | | | - Jens Herfort
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Michael Hanke
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Achim Trampert
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Roman Engel-Herbert
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Manfred Ramsteiner
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
| | - Joao Marcelo J Lopes
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V, 10117, Berlin, Germany
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3
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Muñiz Cano B, Ferreiros Y, Pantaleón PA, Dai J, Tallarida M, Figueroa AI, Marinova V, García-Díez K, Mugarza A, Valenzuela SO, Miranda R, Camarero J, Guinea F, Silva-Guillén JA, Valbuena MA. Experimental Demonstration of a Magnetically Induced Warping Transition in a Topological Insulator Mediated by Rare-Earth Surface Dopants. Nano Lett 2023. [PMID: 37156508 DOI: 10.1021/acs.nanolett.3c00587] [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: 05/10/2023]
Abstract
Magnetic topological insulators constitute a novel class of materials whose topological surface states (TSSs) coexist with long-range ferromagnetic order, eventually breaking time-reversal symmetry. The subsequent bandgap opening is predicted to co-occur with a distortion of the TSS warped shape from hexagonal to trigonal. We demonstrate such a transition by means of angle-resolved photoemission spectroscopy on the magnetically rare-earth (Er and Dy) surface-doped topological insulator Bi2Se2Te. Signatures of the gap opening are also observed. Moreover, increasing the dopant coverage results in a tunable p-type doping of the TSS, thereby allowing for a gradual tuning of the Fermi level toward the magnetically induced bandgap. A theoretical model where a magnetic Zeeman out-of-plane term is introduced in the Hamiltonian governing the TSS rationalizes these experimental results. Our findings offer new strategies to control magnetic interactions with TSSs and open up viable routes for the realization of the quantum anomalous Hall effect.
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Affiliation(s)
- Beatriz Muñiz Cano
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Yago Ferreiros
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Pierre A Pantaleón
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Ji Dai
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
| | - Massimo Tallarida
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
| | - Adriana I Figueroa
- Departament de Física de la Matéria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
| | - Vera Marinova
- Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bontchev, Str. 109, 1113 Sofia, Bulgaria
| | - Kevin García-Díez
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
| | - Aitor Mugarza
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
- ICREA Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010 Barcelona, Spain
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
- ICREA Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010 Barcelona, Spain
| | - Rodolfo Miranda
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto "Nicolás Cabrera" and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid (UAM), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Julio Camarero
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto "Nicolás Cabrera" and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid (UAM), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Francisco Guinea
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Jose Angel Silva-Guillén
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Miguel A Valbuena
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
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4
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Figueroa AI, Bonell F, Cuxart MG, Valvidares M, Gargiani P, van der Laan G, Mugarza A, Valenzuela SO. Absence of Magnetic Proximity Effect at the Interface of Bi_{2}Se_{3} and (Bi,Sb)_{2}Te_{3} with EuS. Phys Rev Lett 2020; 125:226801. [PMID: 33315425 DOI: 10.1103/physrevlett.125.226801] [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] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 09/02/2020] [Accepted: 10/16/2020] [Indexed: 06/12/2023]
Abstract
We performed x-ray magnetic circular dichroism (XMCD) measurements on heterostructures comprising topological insulators (TIs) of the (Bi,Sb)_{2}(Se,Te)_{3} family and the magnetic insulator EuS. XMCD measurements allow us to investigate element-selective magnetic proximity effects at the very TI/EuS interface. A systematic analysis reveals that there is neither significant induced magnetism within the TI nor an enhancement of the Eu magnetic moment at such interface. The induced magnetic moments in Bi, Sb, Te, and Se sites are lower than the estimated detection limit of the XMCD measurements of ∼10^{-3} μ_{B}/at.
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Affiliation(s)
- A I Figueroa
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - F Bonell
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - M G Cuxart
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Universitat Autònoma de Barcelona (UAB), Bellaterra 08193, Spain
| | - M Valvidares
- ALBA Synchrotron Light Source, Barcelona 08290, Spain
| | - P Gargiani
- ALBA Synchrotron Light Source, Barcelona 08290, Spain
| | - G van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - A Mugarza
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
| | - S O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
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5
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Bonell F, Goto M, Sauthier G, Sierra JF, Figueroa AI, Costache MV, Miwa S, Suzuki Y, Valenzuela SO. Control of Spin-Orbit Torques by Interface Engineering in Topological Insulator Heterostructures. Nano Lett 2020; 20:5893-5899. [PMID: 32584582 DOI: 10.1021/acs.nanolett.0c01850] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
(Bi1-xSbx)2Te3 topological insulators (TIs) are gathering increasing attention owing to their large charge-to-spin conversion efficiency and the ensuing spin-orbit torques (SOTs) that can be used to manipulate the magnetization of a ferromagnet (FM). The origin of the torques, however, remains elusive, while the implications of hybridized states and the strong material intermixing at the TI/FM interface are essentially unexplored. By combining interface chemical analysis and spin-transfer ferromagnetic resonance (ST-FMR) measurements, we demonstrate that intermixing plays a critical role in the generation of SOTs. By inserting a suitable normal metal spacer, material intermixing is reduced and the TI properties at the interface are largely improved, resulting in strong variations in the nature of the SOTs. A dramatic enhancement of a field-like torque, opposing and surpassing the Oersted-field torque, is observed, which can be attributed to the non-equilibrium spin density in Rashba-split surface bands and to the suppression of spin memory loss. These phenomena can play a relevant role at other interfaces, such as those comprising transition metal dichalcogenides.
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Affiliation(s)
- Frédéric Bonell
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Minori Goto
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Guillaume Sauthier
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Juan F Sierra
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Adriana I Figueroa
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Marius V Costache
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Shinji Miwa
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yoshishige Suzuki
- Graduate School of Engineering Science and Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08070 Barcelona, Spain
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6
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Sundman A, Vitzthum AL, Adaktylos-Surber K, Figueroa AI, van der Laan G, Daus B, Kappler A, Byrne JM. Effect of Fe-metabolizing bacteria and humic substances on magnetite nanoparticle reactivity towards arsenic and chromium. J Hazard Mater 2020; 384:121450. [PMID: 31759758 DOI: 10.1016/j.jhazmat.2019.121450] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/08/2019] [Accepted: 10/09/2019] [Indexed: 06/10/2023]
Abstract
Magnetite is a magnetic, Fe(II)-Fe(III)-mineral formed through abiogenic and biogenic pathways. It constitutes an attractive material for remediation due to its reactivity, large surface-area-to-volume ratio when present as nanoparticles, and magnetic recoverability. Magnetite can be repeatedly microbially oxidized or reduced, but it is unclear how this influences the reactivity of magnetite towards toxic metal or metalloid contaminants. In this study, magnetite (both abiogenic and biogenic) was exposed to microbial Fe(II) oxidation and Fe(III) reduction, before reacted with hexavalent chromium (Cr(VI)) or pentavalent arsenic (As(V)). Results showed microbial reduction of both magnetite types improved the removal rate of Cr(VI) from solution, though surprisingly microbial Fe(II)-oxidation also showed enhanced reactivity towards Cr(VI) compared to un-treated magnetite. Synchrotron based analysis confirmed the formation of Cr(III) at the surface of the magnetite. Reactivity with As was less dramatic and showed un-treated material was able to remove As(V) from solution faster than microbially Fe(III)-reduced and Fe(II)-oxidized magnetite. The presence of humic substances was also shown to lead to a decreased reactivity of biogenic and abiogenic magnetite towards As(V) and Cr(VI). Our results imply that Fe-metabolizing bacteria influence the immobilization of contaminants and should be considered when evaluating remediation schemes, especially where Fe-metabolizing bacteria are active.
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Affiliation(s)
- Anneli Sundman
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
| | - Anna-Lena Vitzthum
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
| | - Konstantin Adaktylos-Surber
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
| | | | | | - Birgit Daus
- Department Analytical Chemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
| | - James M Byrne
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany.
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7
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Burn DM, Duffy LB, Fujita R, Zhang SL, Figueroa AI, Herrero-Martin J, van der Laan G, Hesjedal T. Cr 2Te 3 Thin Films for Integration in Magnetic Topological Insulator Heterostructures. Sci Rep 2019; 9:10793. [PMID: 31346229 PMCID: PMC6658498 DOI: 10.1038/s41598-019-47265-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [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: 03/28/2019] [Accepted: 07/12/2019] [Indexed: 11/09/2022] Open
Abstract
Chromium telluride compounds are promising ferromagnets for proximity coupling to magnetic topological insulators (MTIs) of the Cr-doped (Bi,Sb)2(Se,Te)3 class of materials as they share the same elements, thus simplifying thin film growth, as well as due to their compatible crystal structure. Recently, it has been demonstrated that high quality (001)-oriented Cr2Te3 thin films with perpendicular magnetic anisotropy can be grown on c-plane sapphire substrate. Here, we present a magnetic and soft x-ray absorption spectroscopy study of the chemical and magnetic properties of Cr2Te3 thin films. X-ray magnetic circular dichroism (XMCD) measured at the Cr L2,3 edges gives information about the local electronic and magnetic structure of the Cr ions. We further demonstrate the overgrowth of Cr2Te3 (001) thin films by high-quality Cr-doped Sb2Te3 films. The magnetic properties of the layers have been characterized and our results provide a starting point for refining the physical models of the complex magnetic ordering in Cr2Te3 thin films, and their integration into advanced MTI heterostructures for quantum device applications.
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Affiliation(s)
- D M Burn
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - L B Duffy
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.,ISIS, Rutherford Appleton Laboratory, Science and Technology Facilities Council, Oxon, OX11 0QX, United Kingdom
| | - R Fujita
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.,Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
| | - S L Zhang
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
| | - A I Figueroa
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.,Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Campus UAB, Barcelona, 08193, Spain
| | - J Herrero-Martin
- CELLS-Divisió Experiments, ALBA Synchrotron Light Source, E-08290 Cerdanyola del Vallès, Barcelona, Catalonia, Spain
| | - G van der Laan
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - T Hesjedal
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
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8
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Kimber RL, Lewis EA, Parmeggiani F, Smith K, Bagshaw H, Starborg T, Joshi N, Figueroa AI, van der Laan G, Cibin G, Gianolio D, Haigh SJ, Pattrick RAD, Turner NJ, Lloyd JR. Biosynthesis and Characterization of Copper Nanoparticles Using Shewanella oneidensis: Application for Click Chemistry. Small 2018; 14. [PMID: 29359400 DOI: 10.1002/smll.201703145] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/23/2017] [Indexed: 05/20/2023]
Abstract
Copper nanoparticles (Cu-NPs) have a wide range of applications as heterogeneous catalysts. In this study, a novel green biosynthesis route for producing Cu-NPs using the metal-reducing bacterium, Shewanella oneidensis is demonstrated. Thin section transmission electron microscopy shows that the Cu-NPs are predominantly intracellular and present in a typical size range of 20-40 nm. Serial block-face scanning electron microscopy demonstrates the Cu-NPs are well-dispersed across the 3D structure of the cells. X-ray absorption near-edge spectroscopy and extended X-ray absorption fine-structure spectroscopy analysis show the nanoparticles are Cu(0), however, atomic resolution images and electron energy loss spectroscopy suggest partial oxidation of the surface layer to Cu2 O upon exposure to air. The catalytic activity of the Cu-NPs is demonstrated in an archetypal "click chemistry" reaction, generating good yields during azide-alkyne cycloadditions, most likely catalyzed by the Cu(I) surface layer of the nanoparticles. Furthermore, cytochrome deletion mutants suggest a novel metal reduction system is involved in enzymatic Cu(II) reduction and Cu-NP synthesis, which is not dependent on the Mtr pathway commonly used to reduce other high oxidation state metals in this bacterium. This work demonstrates a novel, simple, green biosynthesis method for producing efficient copper nanoparticle catalysts.
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Affiliation(s)
- Richard L Kimber
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
| | - Edward A Lewis
- School of Materials, University of Manchester, Manchester, M13 9PL, UK
| | - Fabio Parmeggiani
- School of Chemistry, Manchester Institute of Biotechnology, University of Manchester, Manchester, M1 7DN, UK
| | - Kurt Smith
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
| | - Heath Bagshaw
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
| | - Toby Starborg
- Wellcome Centre for Cell Matrix Research, University of Manchester, Manchester, M13 9PT, UK
| | - Nimisha Joshi
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
| | - Adriana I Figueroa
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire, OX11 0DE, UK
| | - Gerrit van der Laan
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire, OX11 0DE, UK
| | | | | | - Sarah J Haigh
- School of Materials, University of Manchester, Manchester, M13 9PL, UK
| | - Richard A D Pattrick
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
| | - Nicholas J Turner
- School of Chemistry, Manchester Institute of Biotechnology, University of Manchester, Manchester, M1 7DN, UK
| | - Jonathan R Lloyd
- School of Earth and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, M13 9PL, UK
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9
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Figueroa AI, van der Laan G, Harrison SE, Cibin G, Hesjedal T. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films. Sci Rep 2016; 6:22935. [PMID: 26956771 PMCID: PMC4783712 DOI: 10.1038/srep22935] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [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: 12/01/2015] [Accepted: 02/25/2016] [Indexed: 11/23/2022] Open
Abstract
The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state.
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Affiliation(s)
- A I Figueroa
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - G van der Laan
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - S E Harrison
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.,Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA
| | - G Cibin
- Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - T Hesjedal
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.,Diamond Light Source, Didcot, OX11 0DE, United Kingdom
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10
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Baker AA, Figueroa AI, Love CJ, Cavill SA, Hesjedal T, van der Laan G. Anisotropic Absorption of Pure Spin Currents. Phys Rev Lett 2016; 116:047201. [PMID: 26871353 DOI: 10.1103/physrevlett.116.047201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Indexed: 06/05/2023]
Abstract
Spin transfer in magnetic multilayers offers the possibility of ultrafast, low-power device operation. We report a study of spin pumping in spin valves, demonstrating that a strong anisotropy of spin pumping from the source layer can be induced by an angular dependence of the total Gilbert damping parameter, α, in the spin sink layer. Using lab- and synchrotron-based ferromagnetic resonance, we show that an in-plane variation of damping in a crystalline Co_{50}Fe_{50} layer leads to an anisotropic α in a polycrystalline Ni_{81}Fe_{19} layer. This anisotropy is suppressed above the spin diffusion length in Cr, which is found to be 8 nm, and is independent of static exchange coupling in the spin valve. These results offer a valuable insight into the transmission and absorption of spin currents, and a mechanism by which enhanced spin torques and angular control may be realized for next-generation spintronic devices.
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Affiliation(s)
- A A Baker
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE, United Kingdom
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - A I Figueroa
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE, United Kingdom
| | - C J Love
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE, United Kingdom
- Department of Physics, University of York, York YO10 5DD, United Kingdom
| | - S A Cavill
- Department of Physics, University of York, York YO10 5DD, United Kingdom
- Diamond Light Source, Didcot OX11 0DE, United Kingdom
| | - T Hesjedal
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
- Diamond Light Source, Didcot OX11 0DE, United Kingdom
| | - G van der Laan
- Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE, United Kingdom
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11
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Harrison SE, Collins-McIntyre LJ, Zhang SL, Baker AA, Figueroa AI, Kellock AJ, Pushp A, Parkin SSP, Harris JS, van der Laan G, Hesjedal T. Study of Dy-doped Bi₂Te₃: thin film growth and magnetic properties. J Phys Condens Matter 2015; 27:245602. [PMID: 26000785 DOI: 10.1088/0953-8984/27/24/245602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Breaking the time-reversal symmetry (TRS) in topological insulators (TIs) through ferromagnetic doping is an essential prerequisite for unlocking novel physical phenomena and exploring potential device applications. Here, we report the successful growth of high-quality (Dy(x)Bi(1-x))2Te3 thin films with Dy concentrations up to x = 0.355 by molecular beam epitaxy. Bulk-sensitive magnetisation studies using superconducting quantum interference device magnetometry find paramagnetic behaviour down to 2 K for the entire doping series. The effective magnetic moment, μeff, is strongly doping concentration-dependent and reduces from ∼12.6 μ(B) Dy(-1) for x = 0.023 to ∼4.3 μ(B) Dy(-1) for x = 0.355. X-ray absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Dy M4,5 edge are employed to provide a deeper insight into the magnetic nature of the Dy(3+)-doped films. XMCD, measured in surface-sensitive total-electron-yield detection, gives μ(eff )= 4.2 μ(B) Dy(-1). The large measured moments make Dy-doped films interesting TI systems in which the TRS may be broken via the proximity effect due to an adjacent ferromagnetic insulator.
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Affiliation(s)
- S E Harrison
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK. Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
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13
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Bonilla CM, Herrero-Albillos J, Figueroa AI, Castán-Guerrero C, Bartolomé J, Calvo-Almazán I, Schmitz D, Weschke E, García LM, Bartolomé F. Parimagnetism in HoCo2 and TmCo2. J Phys Condens Matter 2014; 26:156001. [PMID: 24675016 DOI: 10.1088/0953-8984/26/15/156001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
X-ray magnetic circular dichroism (XMCD), longitudinal (χac) and transverse (TS) ac magnetic susceptibility have been measured in the RCo2 series (R = Ho, and Tm) as a function of temperature and applied magnetic field. We show that parimagnetism is a general behavior among the RCo2 ferrimagnetic series (R being a heavy rare-earth ion). XMCD results supply evidence of the presence of two compensation temperatures above Tc, defining two different parimagnetic configurations, which is a fully unexpected result. The inverse χ'ac curve exhibits a small anomaly which vanishes under low applied magnetic fields. The combination of TS and XMCD measurements allows one to depict new magnetic phase diagrams for these compounds of the RCo2 series. A new scenario allowing one to understand the observed phenomenology as a Griffiths phase-like behavior is proposed, where the amorphous RCo2 represents the undiluted system case.
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Affiliation(s)
- C M Bonilla
- Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain
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14
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Figueroa AI, Moya C, Bartolomé J, Bartolomé F, García LM, Pérez N, Labarta A, Batlle X. SiO2 coating effects in the magnetic anisotropy of Fe3-xO4 nanoparticles suitable for bio-applications. Nanotechnology 2013; 24:155705. [PMID: 23518930 DOI: 10.1088/0957-4484/24/15/155705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present radio frequency transverse susceptibility (TS) measurements on oleic acid-coated and SiO2-coated Fe3-xO4 magnetite nanoparticles. The effects of the type of coating on the interparticle interactions and magnetic anisotropy are evaluated for two different particle sizes in powder samples. On the one hand, SiO2 coating reduces the interparticle interactions as compared to oleic acid coating, the reduction being more effective for 5 nm than for 14 nm diameter particles. On the other hand, the magnetic anisotropy field at low temperature is lower than 1 kOe in all cases and independent of the coating used. Our results are relevant concerning applications in biomedicine, since the SiO2 coating renders 5 and 14 nm hydrophilic particles with very limited agglomeration, low anisotropy, and superparamagnetic behavior at room temperature. The TS technique also allows us to discriminate the influence on the anisotropy field of interparticle interactions from that of the thermal fluctuations.
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Affiliation(s)
- A I Figueroa
- Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Zaragoza, Spain.
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15
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Bartolomé J, Bartolomé F, García LM, Figueroa AI, Repollés A, Martínez-Pérez MJ, Luis F, Magén C, Selenska-Pobell S, Pobell F, Reitz T, Schönemann R, Herrmannsdörfer T, Merroun M, Geissler A, Wilhelm F, Rogalev A. Strong paramagnetism of gold nanoparticles deposited on a Sulfolobus acidocaldarius S layer. Phys Rev Lett 2012; 109:247203. [PMID: 23368371 DOI: 10.1103/physrevlett.109.247203] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Indexed: 06/01/2023]
Abstract
Magnetic properties of Au nanoparticles deposited on an archaeal S layer are reported. X-ray magnetic circular dichroism and superconducting quantum interference device magnetometries demonstrate that the particles are strongly paramagnetic, without any indication of magnetic blocking down to 16 mK. The average magnetic moment per particle is M(part)=2.36(7) μ(B). This contribution originates at the particle's Au 5d band, in which an increased number of holes with respect to the bulk value is observed. The magnetic moment per Au atom is 25 times larger than any measured in other Au nanoparticles or any other configurations up to date.
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Affiliation(s)
- J Bartolomé
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain.
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