Longitudinal response of spin system of metal on modulated EPR saturation at arbitrary modulation frequency and misalignment of saturated field

The theory on the longitudinal (relative to the external magnetic field) response of the combined system of the localized paramagnetic centers s and free charge carriers e of solid conductor on the modulated saturation of the electron paramagnetic resonance (EPR) is developed. The above consideration is accomplished for the general case of the arbitrary modulation frequencies and misalignments of the SHF-field relative to the EPR central frequency. The theoretical approach based on the separation of the normal modes by the analysis of the bound oscillations of the spin magnetizations of the s and e subsystems is applied. It is shown that under the conditions of the relaxation bond between the subsystems the longitudinal response registered on the modulation frequency may be represented in the form of the sum of the responses from the normal modes. The simple analytical formulae are obtained in the threshold cases of the weak and strong bond