From a study of the influence of uniaxial pressure on the ESR spectrum of "cubic" paramagnetic Fe3+ centres in KTaO,, their spin-phonon coefficients G , , = 1.28 x lo-, eV and G,, 5 0.74 x lo-, eV are determined. The dilatation part of the deformation tensor 51, = 1.4 eV of the Li' off-centre ion in KTaO, is obtained as a result of the study of the elastic broadening of the ESR line caused by the deformation fields of the Li' ions. It is shown that the deformation mechanism makes a substantial contribution to the ESR linewidth of these centres in K, -,Li,TaO,.

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