Spin noise at electron paramagnetic resonance

We develop a microscopic theory of spin noise in solid-state systems at electron paramagnetic resonance, when the spin dynamics is driven by static and radio-frequency (rf) magnetic fields and the stochastic effective magnetic field stemming from the interaction with environment. The rf field splits the peaks in the power spectrum of spin noise into the Mollow-type triplets and also gives rise to additional spin-spin correlations which oscillate in the absolute time at the rf frequency and the double frequency. Even in systems with strong inhomogeneous broadening, the spin-noise spectrum contains narrow lines insensitive to the dispersion of the effective $g$ factors. Thus, the measurements of spin noise at electron paramagnetic resonance provide an access to the intrinsic spin lifetime of electrons.