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Di K, Feng SX, Piramanayagam SN, Zhang VL, Lim HS, Ng SC, Kuok MH. Enhancement of spin-wave nonreciprocity in magnonic crystals via synthetic antiferromagnetic coupling. Sci Rep 2015; 5:10153. [PMID: 25950082 PMCID: PMC4423564 DOI: 10.1038/srep10153] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [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: 01/05/2015] [Accepted: 03/31/2015] [Indexed: 11/29/2022] Open
Abstract
Spin-wave nonreciprocity arising from dipole-dipole interaction is insignificant for magnon wavelengths in the sub-100 nm range. Our micromagnetic simulations reveal that for the nanoscale magnonic crystals studied, such nonreciprocity can be greatly enhanced via synthetic antiferromagnetic coupling. The nonreciprocity is manifested as highly asymmetric magnon dispersion curves of the magnonic crystals. Furthermore, based on the study of the dependence of the nonreciprocity on an applied magnetic field, the antiparallel alignment of the magnetizations is shown to be responsible for the enhancement. Our findings would be useful for magnonic and spintronics applications.
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Affiliation(s)
- K. Di
- Department of Physics, National University of Singapore, Singapore 117551
| | - S. X. Feng
- Department of Physics, National University of Singapore, Singapore 117551
| | - S. N. Piramanayagam
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - V. L. Zhang
- Department of Physics, National University of Singapore, Singapore 117551
| | - H. S. Lim
- Department of Physics, National University of Singapore, Singapore 117551
| | - S. C. Ng
- Department of Physics, National University of Singapore, Singapore 117551
| | - M. H. Kuok
- Department of Physics, National University of Singapore, Singapore 117551
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Di K, Lim HS, Zhang VL, Kuok MH, Ng SC, Cottam MG, Nguyen HT. Comment on "Physical origin and generic control of magnonic band gaps of dipole-exchange spin waves in width-modulated nanostrip waveguides". Phys Rev Lett 2013; 111:149701. [PMID: 24138279 DOI: 10.1103/physrevlett.111.149701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Indexed: 06/02/2023]
Affiliation(s)
- K Di
- Department of Physics, National University of Singapore, Singapore 117542
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Zhang VL, Wang ZK, Lim HS, Ng SC, Kuok MH, Jain S, Adeyeye AO. Nanostructured magnonic crystal with magnetic-field tunable bandgap. J Nanosci Nanotechnol 2011; 11:2657-2660. [PMID: 21449448 DOI: 10.1166/jnn.2011.2730] [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: 05/30/2023]
Abstract
Most experimental investigations into magnonic bandgaps are based on structures composed of single-constituent magnetic materials. Here we report Brillouin and numerical studies of the spin dynamics of a bi-component magnonic crystal, viz. a one-dimensional periodic array of alternating permalloy and cobalt 150 nm-wide nanostripes. Our measurements, together with those for a similar crystal composed of 250 nm-wide nanostripes, suggest that for a stripe width ratio of 1:1, the bandgap width of such magnonic arrays increases with crystal lattice constant. The bandgap parameters are strongly dependent on external magnetic field. This magnetic-field tunability of the bandgap is expected to be a crucial property of devices based on magnonic crystals. The agreement between numerical calculations, based on finite element analysis, and the experimental data is generally good.
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Affiliation(s)
- V L Zhang
- Department of Physics, National University of Singapore, 117542, Singapore
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Lin CS, Lim HS, Wang ZK, Ng SC, Kuok MH, Adeyeye AO. Magnetic field dependence of the lowest-frequency edge-localized spin wave mode in a magnetic nanotriangle. J Nanosci Nanotechnol 2011; 11:2615-2618. [PMID: 21449438 DOI: 10.1166/jnn.2011.2708] [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: 05/30/2023]
Abstract
An understanding of the spin dynamics of nanoscale magnetic elements is important for their applications in magnetic sensing and storage. Inhomogeneity of the demagnetizing field in a non-ellipsoidal magnetic element results in localization of spin waves near the edge of the element. However, relative little work has been carried out to investigate the effect of the applied magnetic fields on the nature of such localized modes. In this study, micromagnetic simulations are performed on an equilateral triangular nanomagnet to investigate the magnetic field dependence of the mode profiles of the lowest-frequency spin wave. Our findings reveal that the lowest-frequency mode is localized at the base edge of the equilateral triangle. The characteristics of its mode profile change with the ground state magnetization configuration of the nanotriangle, which, in turn, depends on the magnitude of the in-plane applied magnetic field.
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Affiliation(s)
- C S Lin
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
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Affiliation(s)
- E. T. Kang
- Department of Chemical Engineering, National University of Singapore, Kent Ridge, Singapore, 0511
| | - K. G. Neoh
- Department of Chemical Engineering, National University of Singapore, Kent Ridge, Singapore, 0511
| | - K. L. Tan
- Department of Physics, National University of Singapore, Kent Ridge, Singapore, 0511
| | - M. H. Kuok
- Department of Physics, National University of Singapore, Kent Ridge, Singapore, 0511
| | - B. T. G. Tan
- Department of Physics, National University of Singapore, Kent Ridge, Singapore, 0511
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Wang ZK, Lim HS, Liu HY, Ng SC, Kuok MH, Tay LL, Lockwood DJ, Cottam MG, Hobbs KL, Larson PR, Keay JC, Lian GD, Johnson MB. Spin waves in nickel nanorings of large aspect ratio. Phys Rev Lett 2005; 94:137208. [PMID: 15904029 DOI: 10.1103/physrevlett.94.137208] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Indexed: 05/02/2023]
Abstract
The spin dynamics of high-aspect-ratio nickel nanorings in a longitudinal magnetic field have been investigated by Brillouin spectroscopy and the results are compared with a macroscopic theory and three-dimensional micromagnetic simulations. Good agreement is found between the measured and calculated magnetic field dependence of the spin wave frequency. Simulations show that as the field decreases from saturation, the rings switch from a "bamboo" to a novel "twisted bamboo" state at a certain critical field, and predict a corresponding dip in the dependence of the spin wave frequency on the magnetic field.
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Affiliation(s)
- Z K Wang
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
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Wilkinson JM, Kuok MH, Adamson G. Biomedical applications of optical imaging. Med Device Technol 2004; 15:22-4. [PMID: 16225280] [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] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Developments in imaging offer real-time visualisation of biological processes at the cellular and molecular level. This article considers how micro- and nanotechnology may enhance the application of optical imaging for in vivo and in vitro diagnostics.
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Affiliation(s)
- J M Wilkinson
- Healthcare and Life Sciences, Technology for Industry Ltd, Ely, UK
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Kuok MH, Lim HS, Ng SC, Liu NN, Wang ZK. Brillouin study of the quantization of acoustic modes in nanospheres. Phys Rev Lett 2003; 90:255502. [PMID: 12857142 DOI: 10.1103/physrevlett.90.255502] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2003] [Indexed: 05/24/2023]
Abstract
The vibrational modes in three-dimensional ordered arrays of unembedded SiO2 nanospheres have been studied by Brillouin light scattering. Multiple distinct Brillouin peaks are observed whose frequencies are found to be inversely proportional to the diameter (approximately 200-340 nm) of the nanospheres, in agreement with Lamb's theory. This is the first Brillouin observation of acoustic mode quantization in a nanoparticle arising from spatial confinement. The distinct spectral peaks measured afford an unambiguous assignment of seven surface and inner acoustic modes. Interestingly, the relative intensities and polarization dependence of the Brillouin spectrum do not agree with the predictions made for Raman scattering.
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Affiliation(s)
- M H Kuok
- Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore.
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Wang ZK, Kuok MH, Ng SC, Lockwood DJ, Cottam MG, Nielsch K, Wehrspohn RB, Gösele U. Spin-wave quantization in ferromagnetic nickel nanowires. Phys Rev Lett 2002; 89:027201. [PMID: 12097013 DOI: 10.1103/physrevlett.89.027201] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Indexed: 05/23/2023]
Abstract
The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires. The results show that it is important to take proper account of these effects for the fundamental physics and future technological developments of magnetic nanowires.
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Affiliation(s)
- Z K Wang
- Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore
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Jones GD, Kuok MH. Zeeman Raman scattering and Zeeman infrared absorption spectra of divalent cobalt ions in several double-chloride crystals. ACTA ACUST UNITED AC 2001. [DOI: 10.1088/0022-3719/12/4/017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Shen ZX, Hu ZP, Chong TC, Beh CY, Tang SH, Kuok MH. Pressure-induced strong mode coupling and phase transitions in KNbO3. Phys Rev B Condens Matter 1995; 52:3976-3980. [PMID: 9981522 DOI: 10.1103/physrevb.52.3976] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kuok MH, Ng SC, Lockwood DJ. Brillouin spectroscopic evidence for a relaxation mode in ferroelectric PbHPO4 and PbDPO4. Phys Rev B Condens Matter 1995; 51:8005-8011. [PMID: 9977408 DOI: 10.1103/physrevb.51.8005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Shen ZX, Ong CW, Tang SH, Kuok MH. Spectroscopic evidence of pressure-induced amorphization in alpha -NaVO3. Phys Rev B Condens Matter 1994; 49:1433-1436. [PMID: 10010456 DOI: 10.1103/physrevb.49.1433] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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