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Magnonic band structure investigation of one-dimensional bi-component magnonic crystal waveguides.

Ma FS, Lim HS, Zhang VL, Ng SC, Kuok MH - Nanoscale Res Lett (2012)

Bottom Line: Our results show that the widths and center frequencies of the bandgaps are controllable by the component materials, the stripe widths, and the orientation of the applied magnetic field.One salient feature of the bandgap frequency plot against stripe width is that there are n-1 zero-width gaps for the nth bandgap for both transversely and longitudinally magnetized waveguides.Additionally, the largest bandgap widths are primarily dependent on the exchange constant contrast between the component materials of the nanostructured waveguides.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National University of Singapore, Singapore, 117542, Singapore. phylimhs@nus.edu.sg.

ABSTRACT
The magnonic band structures for exchange spin waves propagating in one-dimensional magnonic crystal waveguides of different material combinations are investigated using micromagnetic simulations. The waveguides are periodic arrays of alternating nanostripes of different ferromagnetic materials. Our results show that the widths and center frequencies of the bandgaps are controllable by the component materials, the stripe widths, and the orientation of the applied magnetic field. One salient feature of the bandgap frequency plot against stripe width is that there are n-1 zero-width gaps for the nth bandgap for both transversely and longitudinally magnetized waveguides. Additionally, the largest bandgap widths are primarily dependent on the exchange constant contrast between the component materials of the nanostructured waveguides.

No MeSH data available.


Bandgap diagram with respect toM/afor longitudinally magnetized MCWs. With a (=M + N) = 20 nm for (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and (f) MCo/NFe MCWs under applied field H = 600 mT. The gray regions represent the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.
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Figure 5: Bandgap diagram with respect toM/afor longitudinally magnetized MCWs. With a (=M + N) = 20 nm for (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and (f) MCo/NFe MCWs under applied field H = 600 mT. The gray regions represent the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.

Mentions: The dependencies of the magnonic bandgaps on the width M of the stripe with the lattice constant a (=M + N) kept fixed at 20 nm were also investigated for longitudinally magnetized MCWs. The characteristics of the first three bandgaps, obtained at the BZ boundaries (q = π/a, 2π/a, and 3π/a) as a function of M/a for H = 600 mT, are displayed in Figure 5. The feature reported for transversely magnetized MCWs, viz. that the nth bandgap has n-1 zero-gaps, is also exhibited by all the six MCWs, as shown in Figure 5. For the MFe/NNi MCWs, the first bandgap exists over almost the entire range of Fe stripe widths from 0 to 20 nm, and its maximal width of 42.0 GHz appears at M/a = 0.3. For the second bandgap, there is one zero-gap at M/a = 0.4 and two local maximal widths, viz. 59.0 GHz at M/a = 0.2 and 49.5 GHz at M/a = 0.7. For the third bandgap, there are two zero-gaps at M/a = 0.25 and 0.6 and three local maximal widths, viz. 79.0 GHz at M/a = 0.1, 75.0 GHz at M/a = 0.4, and 61.5 GHz at M/a = 0.8.


Magnonic band structure investigation of one-dimensional bi-component magnonic crystal waveguides.

Ma FS, Lim HS, Zhang VL, Ng SC, Kuok MH - Nanoscale Res Lett (2012)

Bandgap diagram with respect toM/afor longitudinally magnetized MCWs. With a (=M + N) = 20 nm for (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and (f) MCo/NFe MCWs under applied field H = 600 mT. The gray regions represent the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475054&req=5

Figure 5: Bandgap diagram with respect toM/afor longitudinally magnetized MCWs. With a (=M + N) = 20 nm for (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and (f) MCo/NFe MCWs under applied field H = 600 mT. The gray regions represent the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.
Mentions: The dependencies of the magnonic bandgaps on the width M of the stripe with the lattice constant a (=M + N) kept fixed at 20 nm were also investigated for longitudinally magnetized MCWs. The characteristics of the first three bandgaps, obtained at the BZ boundaries (q = π/a, 2π/a, and 3π/a) as a function of M/a for H = 600 mT, are displayed in Figure 5. The feature reported for transversely magnetized MCWs, viz. that the nth bandgap has n-1 zero-gaps, is also exhibited by all the six MCWs, as shown in Figure 5. For the MFe/NNi MCWs, the first bandgap exists over almost the entire range of Fe stripe widths from 0 to 20 nm, and its maximal width of 42.0 GHz appears at M/a = 0.3. For the second bandgap, there is one zero-gap at M/a = 0.4 and two local maximal widths, viz. 59.0 GHz at M/a = 0.2 and 49.5 GHz at M/a = 0.7. For the third bandgap, there are two zero-gaps at M/a = 0.25 and 0.6 and three local maximal widths, viz. 79.0 GHz at M/a = 0.1, 75.0 GHz at M/a = 0.4, and 61.5 GHz at M/a = 0.8.

Bottom Line: Our results show that the widths and center frequencies of the bandgaps are controllable by the component materials, the stripe widths, and the orientation of the applied magnetic field.One salient feature of the bandgap frequency plot against stripe width is that there are n-1 zero-width gaps for the nth bandgap for both transversely and longitudinally magnetized waveguides.Additionally, the largest bandgap widths are primarily dependent on the exchange constant contrast between the component materials of the nanostructured waveguides.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National University of Singapore, Singapore, 117542, Singapore. phylimhs@nus.edu.sg.

ABSTRACT
The magnonic band structures for exchange spin waves propagating in one-dimensional magnonic crystal waveguides of different material combinations are investigated using micromagnetic simulations. The waveguides are periodic arrays of alternating nanostripes of different ferromagnetic materials. Our results show that the widths and center frequencies of the bandgaps are controllable by the component materials, the stripe widths, and the orientation of the applied magnetic field. One salient feature of the bandgap frequency plot against stripe width is that there are n-1 zero-width gaps for the nth bandgap for both transversely and longitudinally magnetized waveguides. Additionally, the largest bandgap widths are primarily dependent on the exchange constant contrast between the component materials of the nanostructured waveguides.

No MeSH data available.