In 2012, we demonstrated that microwave loss in practical microwave dielectrics is dominated by electron paramagnetic resonance transitions at cryogenic temperatures. We later used this understanding to develop "smart"materials that switch Fe-doped Al2O3 (ϵr = 9.8) dielectric ceramics between a low-loss "on state"and a high-loss "off state"at frequencies of ∼12 and ∼19 GHz with a small magnetic field (<100 G). In this report, we extend our work on smart materials to the large dielectric constant (ϵr = 24) host La(Al1-xFex)O3 so that it can be used in compact resonator and filter designs operating at ∼4 GHz to ∼7 GHz. The Fe3+ ions' zero-field splitting energies are determined by the crystal-field parameters D = 1.55 GHz and E = 0 GHz, along with significant contributions from the higher-order terms, B 4 0(-6.467 MHz) and B 4 3 (160 MHz). These switchable dielectrics may have applications in future communication and Doppler technology.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)