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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/aunder applied fieldH = 600 mT. With a (=M + N) = 20 nm for transversely magnetized (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and MCo/NFe MCWs. The gray region represents the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.
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Figure 3: Bandgap diagram with respect toM/aunder applied fieldH = 600 mT. With a (=M + N) = 20 nm for transversely magnetized (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and MCo/NFe MCWs. The gray region represents the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.

Mentions: Simulations were also carried out for transversely magnetized MCWs to study the dependence of the bandgaps on the width M of a stripe that has a larger exchange constant in the MCW with the lattice constant a (= M + N) kept fixed at 20 nm. 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 for the six MCWs are displayed in Figure 3. In Figure 3a, the first bandgap of MFe/NNi MCWs exists over almost the entire range of Fe stripe widths from 0 to 20 nm, and its maximum width of 11 GHz occurs at M/a = 0.6. The second bandgap has a zero-gap (i.e., bandgap with a zero-width) at M/a = 0.5 and two local maximal widths, viz. 43.0 GHz at M/a = 0.2 and 36.0 GHz at M/a = 0.7. For the third bandgap, there are two zero-gaps at M/a = 0.3 and 0.65 and three local maximal widths, viz. 61.5 GHz at M/a = 0.1, 59 GHz at M/a = 0.5, and 52 GHz at M/a = 0.8. This implies that there are n-1 zero-gaps for the nth bandgap. This feature is also exhibited by all the other MCWs as shown in Figure 3a,d,c,d,e,f.


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/aunder applied fieldH = 600 mT. With a (=M + N) = 20 nm for transversely magnetized (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and MCo/NFe MCWs. The gray region represents 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 3: Bandgap diagram with respect toM/aunder applied fieldH = 600 mT. With a (=M + N) = 20 nm for transversely magnetized (a) MFe/NNi, (b) MFe/NPy, (c) MPy/NNi, (d) MCo/NNi, (e) MCo/NPy, and MCo/NFe MCWs. The gray region represents the allowed bands, while the red, green, and blue regions, the respective first, second, and third forbidden bands.
Mentions: Simulations were also carried out for transversely magnetized MCWs to study the dependence of the bandgaps on the width M of a stripe that has a larger exchange constant in the MCW with the lattice constant a (= M + N) kept fixed at 20 nm. 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 for the six MCWs are displayed in Figure 3. In Figure 3a, the first bandgap of MFe/NNi MCWs exists over almost the entire range of Fe stripe widths from 0 to 20 nm, and its maximum width of 11 GHz occurs at M/a = 0.6. The second bandgap has a zero-gap (i.e., bandgap with a zero-width) at M/a = 0.5 and two local maximal widths, viz. 43.0 GHz at M/a = 0.2 and 36.0 GHz at M/a = 0.7. For the third bandgap, there are two zero-gaps at M/a = 0.3 and 0.65 and three local maximal widths, viz. 61.5 GHz at M/a = 0.1, 59 GHz at M/a = 0.5, and 52 GHz at M/a = 0.8. This implies that there are n-1 zero-gaps for the nth bandgap. This feature is also exhibited by all the other MCWs as shown in Figure 3a,d,c,d,e,f.

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.