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1.
Sci Rep ; 5: 10153, 2015 May 07.
Article in English | MEDLINE | ID: mdl-25950082

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.

3.
J Nanosci Nanotechnol ; 11(3): 2615-8, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21449438

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.


Subject(s)
Computer-Aided Design , Magnetics/instrumentation , Models, Theoretical , Nanotechnology/instrumentation , Computer Simulation , Electromagnetic Fields , Equipment Design , Equipment Failure Analysis , Scattering, Radiation
4.
J Nanosci Nanotechnol ; 11(3): 2657-60, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21449448

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.


Subject(s)
Crystallization/methods , Magnetics/instrumentation , Nanostructures/chemistry , Nanotechnology/instrumentation , Equipment Design , Equipment Failure Analysis , Nanostructures/ultrastructure , Particle Size
5.
Phys Rev Lett ; 94(13): 137208, 2005 Apr 08.
Article in English | MEDLINE | ID: mdl-15904029

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.

6.
Med Device Technol ; 15(10): 22-4, 2004 Dec.
Article in English | MEDLINE | ID: mdl-16225280

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.


Subject(s)
Biomedical Engineering/methods , Image Enhancement/methods , Microscopy, Fluorescence/methods , Molecular Biology/methods , Quantum Dots , Tomography, Optical/methods , Biomedical Engineering/instrumentation , Molecular Probe Techniques , Technology Assessment, Biomedical
7.
Phys Rev Lett ; 90(25 Pt 1): 255502, 2003 Jun 27.
Article in English | MEDLINE | ID: mdl-12857142

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.

8.
Phys Rev Lett ; 89(2): 027201, 2002 Jul 08.
Article in English | MEDLINE | ID: mdl-12097013

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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