Direct observation of the precession of individual paramagnetic spins on oxidized silicon surfaces

The precession of individual spins on partially oxidized Si(111) surfaces has been detected using a scanning tunneling microscope. The spin precession in a constant magnetic field induces a modulation in the tunneling current at the Larmor frequency. This radio-frequency signal is shown to be localized over distances less than 10 A{} and follows the expected magnetic field dependence.