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Magnetic-Field-Tunable Intensity Transfer from Optically Active Phonons to Crystal-Field Excitations in the Reflection Spectra of the PrFe3(BO3)4 Antiferromagnet. CRYSTALS 2022. [DOI: 10.3390/cryst12030392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We analyze the field-dependent intensities of the coupled electron-phonon modes observed in the low-temperature far-infrared (terahertz) reflection spectra of PrFe3(BO3)4 and develop a theory based on the Green’s function approach. An excellent agreement between the experimental and theoretical data is achieved. The developed theory of the intensity transfer from phonons to quasi-electronic excitations can be applied to the electron-phonon modes in other compounds, in particular, in magnetodielectric materials, where it can be used to analyze the magnetodielectric response.
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Experimental and Theoretical Investigations of Low-Dimensional BiFeO3 System for Photocatalytic Applications. Catalysts 2022. [DOI: 10.3390/catal12020215] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We report on the fabrication of sub-20 nm BiFeO3 (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of the optical and the photocatalytic properties were conducted to determine the effects of the particles size, the microstructure and the increased surface area on their catalytic performances. Especially, improved optical properties were observed, with an optical bandgap energy of 2.20 eV compared to reported 2.7 eV for the bulk system. In addition, high optical absorption was obtained in the UV–visible light region reaching up to 90% at 400 nm. The photoelectrochemical measurements revealed a high photocurrent density under visible light irradiation. Besides, density functional theory calculations were performed on both bulk and thin film BFO structures, revealing an interesting comparison of the electronic, magnetic, ferroelectric and optical properties for bulk and thin film BFO systems. Both theoretical and experimental findings show that the alignment of the band edges of BFO thin film is coherent with good photocatalytic water splitting potential, making them desirable photoanode materials.
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Vít J, Viirok J, Peedu L, Rõõm T, Nagel U, Kocsis V, Tokunaga Y, Taguchi Y, Tokura Y, Kézsmárki I, Balla P, Penc K, Romhányi J, Bordács S. In Situ Electric-Field Control of THz Nonreciprocal Directional Dichroism in the Multiferroic Ba_{2}CoGe_{2}O_{7}. PHYSICAL REVIEW LETTERS 2021; 127:157201. [PMID: 34678006 DOI: 10.1103/physrevlett.127.157201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 07/28/2021] [Indexed: 06/13/2023]
Abstract
Nonreciprocal directional dichroism, also called the optical-diode effect, is an appealing functional property inherent to the large class of noncentrosymmetric magnets. However, the in situ electric control of this phenomenon is challenging as it requires a set of conditions to be fulfilled: Special symmetries of the magnetic ground state, spin excitations with comparable magnetic- and electric-dipole activity, and switchable electric polarization. We demonstrate the isothermal electric switch between domains of Ba_{2}CoGe_{2}O_{7} possessing opposite magnetoelectric susceptibilities. Combining THz spectroscopy and multiboson spin-wave analysis, we show that unbalancing the population of antiferromagnetic domains generates the nonreciprocal light absorption of spin excitations.
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Affiliation(s)
- J Vít
- Department of Physics, Budapest University of Technology and Economics, 1111 Budapest, Hungary
- Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8, Czech Republic
- Faculty of Nuclear Science and Physical Engineering, Czech Technical University, Břehová 7, 115 19 Prague 1, Czech Republic
| | - J Viirok
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - L Peedu
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - T Rõõm
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - U Nagel
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
| | - V Kocsis
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Y Tokunaga
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan
| | - Y Taguchi
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Y Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - I Kézsmárki
- Department of Physics, Budapest University of Technology and Economics, 1111 Budapest, Hungary
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - P Balla
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box. 49, H-1525 Budapest, Hungary
| | - K Penc
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box. 49, H-1525 Budapest, Hungary
| | - J Romhányi
- Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, California 92697, USA
| | - S Bordács
- Department of Physics, Budapest University of Technology and Economics, 1111 Budapest, Hungary
- Hungarian Academy of Sciences, Premium Postdoctor Program, 1051 Budapest, Hungary
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Liu C, Luo Y, Hong D, Zhang SSL, Saglam H, Li Y, Lin Y, Fisher B, Pearson JE, Jiang JS, Zhou H, Wen J, Hoffmann A, Bhattacharya A. Electric field control of magnon spin currents in an antiferromagnetic insulator. SCIENCE ADVANCES 2021; 7:eabg1669. [PMID: 34586846 PMCID: PMC8480924 DOI: 10.1126/sciadv.abg1669] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
Pure spin currents can be generated via thermal excitations of magnons. These magnon spin currents serve as carriers of information in insulating materials, and controlling them using electrical means may enable energy efficient information processing. Here, we demonstrate electric field control of magnon spin currents in the antiferromagnetic insulator Cr2O3. We show that the thermally driven magnon spin currents reveal a spin-flop transition in thin-film Cr2O3. Crucially, this spin-flop can be turned on or off by applying an electric field across the thickness of the film. Using this tunability, we demonstrate electric field–induced switching of the polarization of magnon spin currents by varying only a gate voltage while at a fixed magnetic field. We propose a model considering an electric field–dependent spin-flop transition, arising from a change in sublattice magnetizations via a magnetoelectric coupling. These results provide a different approach toward controlling magnon spin current in antiferromagnets.
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Affiliation(s)
- Changjiang Liu
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Yongming Luo
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
- School of Electronics and Information, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China
| | - Deshun Hong
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Steven S.-L. Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
- Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Hilal Saglam
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Yi Li
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Yulin Lin
- Nanoscale Science and Technology Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Brandon Fisher
- Nanoscale Science and Technology Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - John E. Pearson
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - J. Samuel Jiang
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Hua Zhou
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Jianguo Wen
- Nanoscale Science and Technology Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Axel Hoffmann
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
- Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Anand Bhattacharya
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
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Abstract
The polarizing spectroscopy techniques in visible range optics have been used since the beginning of the 20th century to study the anisotropy of crystals based on birefringence and optical activity phenomena. On the other hand, the phenomenon of X-ray optical activity has been demonstrated only relatively recently. It is a selective probe for the element-specific properties of individual atoms in non-centrosymmetric materials. We report the X-ray Natural Circular Dichroism (XNCD) imaging technique which enables spatially resolved mapping of X-ray optical activity in non-centrosymmetric materials. As an example, we present the results of combining micro-focusing X-ray optics with circularly polarized hard X-rays to make a map of enantiomorphous twinning in a multiferroic SmFe3(BO3)4 crystal. Our results demonstrate the utility and potential of polarization-contrast imaging with XNCD as a sensitive technique for multiferroic crystals where the local enantiomorphous properties are especially important. In perspective, this brings a novel high-performance method for the characterization of structural changes associated with phase transitions and identification of the size and spatial distribution of twin domains.
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Zhang H, Liu S, Nelson CS, Bezmaternykh LN, Chen YS, Wang SG, Lobo RPSM, Page K, Matsuda M, Pajerowski DM, Williams TJ, Tyson TA. Structural features associated with multiferroic behavior in the RX 3(BO 3) 4 system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:505704. [PMID: 31484172 DOI: 10.1088/1361-648x/ab415f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The magnetoelectric effect in the RX3(BO3)4 system (R = Ho, Eu, Sm, Nd, Gd; X = Fe, Al) varies significantly with the cation R despite very similar structural arrangements. Our structural studies reveal a symmetry reducing tilting of the BO3 planes and of the FeO6 polyhedra in the systems exhibiting low magnetic field induced electric polarization. Neutron scattering measurements reveal a lack of magnetic ordering indicating the primary importance of the atomic structure in the multiferroic behavior of this system.
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Affiliation(s)
- H Zhang
- Department of Physics, New Jersey Institute of Technology, Newark, NJ 071022, United States of America
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Szaller D, Shuvaev A, Mukhin AA, Kuzmenko AM, Pimenov A. Controlling of light with electromagnons. PHYSICAL SCIENCES REVIEWS 2019. [DOI: 10.1515/psr-2019-0055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Magnetoelectric coupling in multiferroic materials opens new routes to control the propagation of light. The new effects arise due to dynamic magnetoelectric susceptibility that cross-couples the electric and magnetic fields of light and modifies the solutions of Maxwell equations in media. In this paper, two major effects will be considered in detail: optical activity and asymmetric propagation. In case of optical activity the polarization plane of the input radiation rotates by an angle proportional to the magnetoelectric susceptibility. The asymmetric propagation is a counter-intuitive phenomenon and it represents different transmission coefficients for forward and backward directions. Both effects are especially strong close to resonance frequencies of electromagnons, i. e. excitations in multiferroic materials that reveal simultaneous electric and magnetic character.
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Affiliation(s)
- D. Szaller
- Institute of Solid State Physics , Vienna University of Technology , Vienna 1040 , Austria
| | - A. Shuvaev
- Institute of Solid State Physics , Vienna University of Technology , Vienna 1040 , Austria
| | - A. A. Mukhin
- Prokhorov General Physics Institute, Russian Academy of Sciences , Moscow 119991 , Russian Federation
| | - A. M. Kuzmenko
- Prokhorov General Physics Institute, Russian Academy of Sciences , Moscow 119991 , Russian Federation
| | - A. Pimenov
- Institute of Solid State Physics , Vienna University of Technology , Vienna 1040 , Austria
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Abstract
Magnonics, an emerging research field, aims to control and manipulate spin waves in magnetic materials and structures. However, the current understanding of spin waves remains quite limited. This review attempts to provide an overview of the anomalous behaviors of spin waves in various types of magnetic materials observed thus far by inelastic light scattering experiments. The anomalously large asymmetry of anti-Stokes to Stokes intensity ratio, broad linewidth, strong resonance effect, unique polarization selection, and abnormal impurity dependence of spin waves are discussed. In addition, the mechanisms of these anomalous behaviors of spin waves are proposed.
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