| The temperature dependence of the EPR spectrum of lithium tetraborate (Li2B4O7) single crystal doped with manganese is presented. Taking into account thermal expansion, contraction, and spin-phonon effects, two anomalous regions of the temperature behaviour were found: one beginning at about 270K and the other at about 365K. This anomalous behaviour seems to correlate very well with the literature data on the results of dielectric measurements. It is suggested that such anomalous behaviour can be adequately interpreted in terms of the so-called modified two-sublattice model of Mitsui in which both short- and long-range interactions of BO4 groups are simultaneously included in the Hamiltonian describing the system. |
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