Axions are hypothetical particles originally proposed to solve the strong CP problem, and their extremely weak interactions make them well-motivated candidates for cold dark matter. The Cosmic Axion Spin Precession Experiment (CASPEr) searches for dark matter axions using nuclear magnetic resonance (NMR) and optical magnetometry. Within the CASPEr program, the CASPEr-gradient search is divided into two regimes: the low-field (LF) experiment, sensitive to axions in the kHz to 1 MHz range, and the high-field (HF) experiment, targeting the 70 MHz to 600 MHz range. In this talk, I will present recent results from the CASPEr-LF experiment and discuss the current status of the CASPEr-HF effort.
Monochromatic high-frequency gravitational waves (HFGWs) offer a unique window into new physics, particularly axion clouds around rotating black holes formed through superradiance. In a strong magnetic field, HFGWs can convert into microwave photons, providing an experimental avenue for detection. I will present recent reanalysis results using existing data from the IBS-CAPP 12 T multicell cavity experiment, and introduce GravNet (Global detector network to search for high-frequency gravitational waves), a new experimental approach for searching for gravitational waves in the GHz frequency range.