Microwave response of strongly demagnetized anisotropic samples

Understanding the electromagnetic response of conducting samples in magnetic fields is necessary to interpret the results of radio- and microwave- frequency experiments. A common geometry used is that of a platelet sample aligned perpendicularly to the applied field, but this induces strong demagnetizing effects that are still the subject of ongoing study because of the difficulty of modelling fields near sharp edges and corners. Furthermore, in materials exhibiting non-local electrodynamics, the surface impedance associated with each face may be different, meaning the weighted contributions from different sample faces to the apparent surface impedance become harder to disentangle.

To support the interpretation of such spectroscopic measurements, the microwave magnetic response of realistic, strongly-demagnetized samples was studied[1] using numerical simulations in COMSOL Multiphysics®. Here we present the results from these studies, and how they were used to determine the non-local surface impedance of palladium cobaltate (PdCoO₂) from microwave spectroscopy measurements. This modelling also has implications for the RF responses of other materials such as non-local anisotropic superconductors [2].

[1] Branch T., Master’s Thesis (2021)

[2] Kosztin, PRL 79, 135 (1997)