ESR spectrum peculiarities in a nano-thin perovskite film

We propose the model for the calculation of electron spin resonance (ESR) spectra of paramagnetic impurities located inside a nano-thin film. As a simplest and typical example we take a d3 ion in a perovskite. In the paraelectric phase we account for the surface influence using the model of image charges. In the ferroelectric phase, we add the effect of inhomogeneous polarization. The dependence of coefficients of the impurity spin Hamiltonian on the distance from the film surface z0 leads to the strongly asymmetric form of the inhomogeneously broadened ESR absorbtion line. In a paraelectric film, the environment of the center near the surface looses the cubic symmetry and the ESR spectrum becomes tetragonal, the axial constant being of the order of 10-4cm-1 and it decreases as z0-3. The ESR spectrum acquires the fine structure, the line splitting depends on film thickness l as l-3. In ferroelectric films the average value of polarization enhances the fine structure line splitting, and the polarization distribution contributes the inhomogeneous line broadening. We calculate the absorption line shapes for different characteristics of both the homogeneous and inhomogeneous mechanisms as well as on the film thickness.