title: A remarkable transformation of magnetic resonance spectra as a result of a mutual influence of coexisting para- and ferromagnetic phases.
abstract: In this work, we carry out the analysis of the resonance absorption of electromagnetic radiation for the system in which para- and ferromagnetic phases coexist over a wide temperature region. It is found that taking account of the mutual influence of coexisting phases gives rise to the appearance of substantial changes in the curves of resonance absorption and values of resonance fields, as well as to making the geometry of a phase distribution dependent on an external magnetic field. Near the temperature boundaries of the phase coexistence region, the expressions for description of the curves of the dispersive absorption of electromagnetic radiation are obtained and the rules of the behaviour of the resonance fields for each of the phases are specified. As follows from the calculations, the resonance field for the paramagnetic phase becomes dependent on the shape of the sample, the saturation magnetization and the fraction of ferromagnetic phase. It is shown that the character of magnetic resonance spectra and the features of their temperature change agree well with the experimental data, obtained by various groups of researchers on the single crystalline and polycrystalline samples of doped perovskite manganites.
authors.affiliation: Institute of Magnetism, 36-b Vernadsky Boulevard, Kyiv 03142, Ukraine.
authors.forename: Yu I
authors.initials: YI
authors.lastname: Dzhezherya
authors.forename: A I
authors.initials: AI
authors.lastname: Tovstolytkin