Rectangular-waveguide dispersion in Damon-Eshbach geometry

In this example, we will calculate the equilibrium state and dispersion relation in a rectangular permalloy waveguide with an 160 nm x 10 nm cross-section under an applied transversal field of 200 mT.

import tetrax as tx

sample = tx.Sample(
    tx.geometries.waveguide.rectangular(
        width = 160,
        thickness = 10,
        cell_size_width = 2,
        cell_size_thickness = 2,
    ),
    name = "rect_Py_WG_160x10"
)

sample.material = tx.materials.permalloy

sample.show()

/Users/attilak/micromag/tetrax-tests/fresh_environement_test/venv/lib/python3.13/site-packages/traittypes/traittypes.py:97: UserWarning: Given trait value dtype "float32" does not match required type "float32". A coerced copy has been created.
  warnings.warn(

Next, we transversally satured the sample. For this, apply the external field and relax it, starting from a homogeneously tilted state. After the relaxation is succeded, we plot its right away.

sample.mag = tx.vectorfields.homogeneous(sample.xyz, theta=60.0, phi=10.0)
sample.external_field = (200e-3, 0, 0)

success = False
while not success:
    relaxation_result = tx.experiments.relax(sample, tolerance=1e-14)
    success = relaxation_result.was_success

relaxation_result.plot(renderer="notebook") # remove the renderer argument when running on your computer

Minimizing energy in using 'L-BFGS-B' (tolerance 1e-14) ...
energy length density: -2.037861670450534e-10 J/m, <mag.x> = 1.00, <mag.y> = -0.00, <mag.z> = 0.00
Success!

Plotting the magnetization shows that we are in the intended state.

sample.show(scale=10)

/Users/attilak/micromag/tetrax-tests/fresh_environement_test/venv/lib/python3.13/site-packages/traittypes/traittypes.py:97: UserWarning:

Given trait value dtype "float32" does not match required type "float32". A coerced copy has been created.

Now, let us calculate the spin-wave spectrum.

spectrum = tx.experiments.eigenmodes(sample, num_cpus=-1,num_modes=10, num_k=81, kmin=0)

100%|███████████████████| 81/81 [00:04<00:00, 17.44it/s]

We plot the dispersion using the built-in plot() method.

spectrum.plot(k=(0,40e6), renderer="notebook") # remove the renderer argument when running on your computer