Sensing Spin Systems with a Transmission Electron Microscope

We present a novel method that combines spin resonance spectroscopy with transmission electron microscopy (TEM), enabling localized in-situ detection of microwave (MW)-driven spin excitations. Our approach utilizes continuous wave MW excitation at GHz frequencies, while employing the free-space electron beam as a signal receiver to sense spin precession. Spin state polarization is achieved via the magnetic field of the TEM's polepiece, while a custom-designed microresonator integrated into a TEM sample holder drives spin transitions and modulates the electron beam. This modulation enables phase-locked detection with picosecond temporal resolution, allowing the isolation of spin precession contributions to the electron beam deflection with a sensitivity of $\sim 280$ prad. The presented technique lays foundations for the MW spectroscopic in-situ exploration of spin dynamics at the nanoscale.