Py-Cu Graded-Index Magnonic Waveguides*

Spin waves (magnons) have many optical analogies, including the law of reflection, which allows total internal reflection (akin to a fiber optic cable). For this reason, we’re working to create a magnonic waveguide made from Py-Cu multilayered films.

We grow films via sputter deposition with a 10 nm core of Py_0.8Cu_0.2 that is symmetrically bound by 10 nm of Cu and 10 nm of Py_0.6Cu_0.4. Py-Cu alloys are attractive for this study because we can easily tune magnetic properties by changing the Cu content of each layer (T_C decreases as Cu content increases).

We measure samples using ferromagnetic resonance (FMR) with frequencies from 3-20 GHz and fit results to the Kittel equation. We extract values for the Gilbert damping parameter and inhomogeneous broadening, which informs us of how magnons propagate through each multilayer film.

Ideally, if we reverse the magnetic layers, instead of seeing total internal reflection, we should observe a complete spin absorber.