Detection of Picosecond Magnetization Dynamics of 50 nm Magnetic Dots down to the Single Dot Regime

Rana, Bivas; Kumar, Dushyant; Barman, Saswati; Pal, Semanti; Fukuma, Yasuhiro; Otani, Y.; Barman, Anjan

doi:10.1021/nn202791g

Cited by 57 publications

(39 citation statements)

References 37 publications

(73 reference statements)

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“…This also shows, that a thin film MC composed of an array of saturated ferromagnetic nanodots can be used as a magnonic metamaterial, i.e., an artificial crystal with tailored effective properties of spin wave dynamics. [36][37][38][39] Further studies are necessary to elucidate the limits of the effective saturation magnetization approach presented here, the influence of the dot-shape, their arrangement and inter-dot separation (mode-splitting has been experimentally demonstrated for nano-dot arrays 40 ), but this is outside the scope of this paper.…”

Section: Resultsmentioning

confidence: 99%

Magnonic band structure, complete bandgap, and collective spin wave excitation in nanoscale two-dimensional magnonic crystals

Kumar

Kłos

Krawczyk

et al. 2014

Journal of Applied Physics

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We present the observation of a complete bandgap and collective spin wave excitation in two-dimensional magnonic crystals comprised of arrays of nanoscale antidots and nanodots, respectively. Considering that the frequencies dealt with here fall in the microwave band, these findings can be used for the development of suitable magnonic metamaterials and spin wave based signal processing. We also present the application of a numerical procedure, to compute the dispersion relations of spin waves for any high symmetry direction in the first Brillouin zone. The results obtained from this procedure has been reproduced and verified by the well established plane wave method for an antidot lattice, when magnetization dynamics at antidot boundaries is pinned. The micromagnetic simulation based method can also be used to obtain iso-frequency countours of spin waves. Iso-frequency contours are analougous of the Fermi surfaces and hence, they have the potential to radicalize our understanding of spin wave dynamics. The physical origin of bands, partial and full magnonic bandgaps has been explained by plotting the spatial distribution of spin wave energy spectral density. Although, unfettered by rigid assumptions and approximations, which afflict most analytical methods used in the study of spin wave dynamics, micromagnetic simulations tend to be computationally demanding. Thus, the observation of collective spin wave excitation in the case of nanodot arrays, which can obviate the need to perform simulations may also prove to be valuable. a) These authors have contributed equally to this work. b) Electronic mail: abarman@bose.res.in arXiv:1312.3044v1 [cond-mat.mes-hall]

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Section: Resultsmentioning

confidence: 99%

Magnonic band structure, complete bandgap, and collective spin wave excitation in nanoscale two-dimensional magnonic crystals

Kumar

Kłos

Krawczyk

et al. 2014

Journal of Applied Physics

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“…The height profiles of the dots were measured by atomic force microscope and the average height was found to be between 20 and 22 nm in different lattices, which agree well with the nominal thickness of the samples. The ultrafast magnetization dynamics of the samples are measured by using a custom built time‐resolved magneto optical Kerr effect microscope based upon a two color collinear pump‐probe setup 28. The magneto‐optical Kerr rotation of the probe beam ( λ = 800 nm, pulsewidth ≈ 70 fs) is measured after excitation by the pump beam ( λ = 400 nm, pulsewidth ≈ 100 fs) as a function of the time delay between the pump and probe beams.…”

Section: Resultsmentioning

confidence: 99%

Tunable Magnonic Spectra in Two‐Dimensional Magnonic Crystals with Variable Lattice Symmetry

Saha

Mandal

Barman

et al. 2012

Adv Funct Materials

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Tunable magnonic properties are demonstrated in two‐dimensional magnonic crystals in the form of artificial ferromagnetic nanodot lattices with variable lattice symmetry. An all‐optical time‐domain excitation and detection of the collective precessional dynamics is performed in the strongly magnetostatically coupled Ni80Fe20 (Py) circular dot lattices arranged in different lattice symmetry such as square, rectangular, hexagonal, honeycomb, and octagonal symmetry. As the symmetry changes from square to octagonal through rectangular, hexagonal and honeycomb, a significant variation in the spin wave spectra is observed. The single uniform collective mode in the square lattice splits in two distinct modes in the rectangular lattice and in three distinct modes in the hexagonal and octagonal lattices. However, in the honeycomb lattice a broad band of modes are observed. Micromagnetic simulations qualitatively reproduce the experimentally observed modes, and the simulated mode profiles reveal collective modes with different spatial distributions with the variation in the lattice symmetry determined by the magnetostatic field profiles. For the hexagonal lattice, the most intense peak shows a six‐fold anisotropy with the variation in the azimuthal angle of the external bias magnetic field. Analysis shows that this is due to the angular variation of the dynamical component of magnetization for this mode, which is directly influenced by the variation of the magnetostatic field on the elements in the hexagonal lattice. The observations are important for tunable and anisotropic propagation of spin waves in magnonic crystal based devices.

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“…8 As a result a new research field named magnonics has emerged which has the capability to replace current semiconductor technology. One important problem is to tune the magnonic band structure of the MCs by varying different geometrical parameters like shape, 9 size, 10 lattice spacing 11 and lattice symmetry 12 and also by changing the constituent ferromagnetic materials. 13 Two dimensional (2-D) periodic ferromagnetic antidot lattices (ADLs) have emerged as potential candidates for magneto-photonic crystals, [14][15] ultra-high density magnetic storage media 16 and magnonic crystals.…”

Section: Introductionmentioning

confidence: 99%

Shape- and Interface-Induced Control of Spin Dynamics of Two-Dimensional Bicomponent Magnonic Crystals

Choudhury

Saha

Mandal

et al. 2016

ACS Appl. Mater. Interfaces

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Controlled fabrication of periodically arranged embedded nanostructures with strong interelement interaction through the interface between the two different materials has great potential applications in spintronics, spin logic, and other spin-based communication devices. Here, we report the fabrication of two-dimensional bicomponent magnonic crystals in form of embedded Ni80Fe20 nanostructures in Co50Fe50 thin films by nanolithography. The spin wave (SW) spectra studied by a broadband ferromagnetic resonance spectroscopy showed a significant variation as the shape of the embedded nanostructure changes from circular to square. Significantly, in both shapes, a minimum in frequency is obtained at a negative value of bias field during the field hysteresis confirming the presence of a strong exchange coupling at the interface between the two materials, which can potentially increase the spin wave propagation velocity in such structures leading to faster gigahertz frequency magnetic communication and logic devices. The spin wave frequencies and bandgaps show bias field tunability, which is important for above device applications. Numerical simulations qualitatively reproduced the experimental results, and simulated mode profiles revealed the spatial distribution of the SW modes and internal magnetic fields responsible for this observation. Development of such controlled arrays of embedded nanostructures with improved interface can be easily applied to other forms of artificial crystals.

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Detection of Picosecond Magnetization Dynamics of 50 nm Magnetic Dots down to the Single Dot Regime

Cited by 57 publications

References 37 publications

Magnonic band structure, complete bandgap, and collective spin wave excitation in nanoscale two-dimensional magnonic crystals

Magnonic band structure, complete bandgap, and collective spin wave excitation in nanoscale two-dimensional magnonic crystals

Tunable Magnonic Spectra in Two‐Dimensional Magnonic Crystals with Variable Lattice Symmetry

Shape- and Interface-Induced Control of Spin Dynamics of Two-Dimensional Bicomponent Magnonic Crystals

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