# Sensing Spin Precession with Free Electrons

## TL;DR

This paper introduces a new method using electron microscopy to detect spin transitions at the nanoscale.

## Contribution

A novel technique combining spin resonance and TEM for localized spin precession sensing is introduced.

## Key findings

- Spin state polarization is achieved using the TEM’s magnetic field.
- MW-driven spin transitions induce electron beam deflection detectable via phase-locked detection.
- The method enables in situ nanoscale exploration of spin excitations.

## Abstract

We present a method that combines spin resonance spectroscopy
with
transmission electron microscopy (TEM), enabling localized in situ detection of microwave (MW)-driven spin transitions
in the specimen, utilizing the free-space electron beam of the TEM
as a signal receiver. 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 delivers continuous
wave MW excitation at GHz frequencies. At resonance, the MW field
drives spin transitions that produce a dynamic, precessional magnetic
field around the specimen, inducing a deflection of the free-space
electron beam. Phase-locked detection synchronized to the MW driving
fields enables the isolation of spin precession contributions to the
electron beam deflection. The presented technique offers a pathway
for the in situ exploration of spin excitations at
the nanoscale.