Simulating antenna width limit on spin wave excitation

[anirban.m...@gmail.com]

Dear MuMax3 community,

A micro-stripline antenna with a width W can excite wavenumbers up to 2π/W. I want to simulate antenna width limitation for MSSWs.

Now, if I have a YIG film of 10 μm x 100 nm x 1 μm:

Nx := 1000
Ny := 10
Nz := 100 

setgridsize(Nx, Ny, Nz)
setcellsize(10e-9, 10e-9, 10e-9)

Msat = 138.46e03
alpha = 0.001
Aex = 3.6e-12 

Now, if I set a rectangular excitation region of 100 nm x 100 nm x 1 μm:

B_ext = 4e-07 * pi * 25e03
fc := 12e9
exc_reg := rect(100e-9, 100e-9)
defRegion(100, exc_reg)
B_ext.SetRegion(100, vector(0,  B0*sinc(2*pi*fc*t), 0)) 

If I set up my simulation in this manner, will I be able to observe the MSSW frequency up to 9 GHz?

I am new to MuMax3, and I would appreciate any suggestions or guidance the community may have regarding my question.

[Антон Луценко]

Hi, 

0. Technically, this antenna can excite higher wave numbers, it's just that the first zero is at 2π/W.

1. For several reasons, you might want to keep your film thickness direction in Z, so I would recommend setting your dimensions Nx = 1000, Ny = 100, Nz = 10 instead. 

2. You would need to set up the magnetic properties for region 1 as well, otherwise they are default and you won't be able to see excitation. For this and several other reasons , I'd recommend switching to vector field antenna rather than regionwise and use B_ext.Add(mask, timemult) instead. 

3. External field must be a vector, not a scalar. So "B_ext = 4e-07 * pi * 25e03" is a mistake. You must set it as vector(Bx, By, Bz), with components in Tesla units. 

Hope that helps!