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The A(1), E(1) and E(2) Raman active modes in hexagonal YMnO(3) and LuMnO(3) single crystals are studied as a function of temperature and compared with previous measurements. In addition to anharmonicity, some phonon frequencies show below T(N) anomalous temperature dependences that reflect the atomic displacements while some other phonon frequencies are more sensitive to the spin-phonon coupling.

ErMnO3 single crystals are studied by polarized first-order and second-order micro-Raman measurements as a function of temperature and compared to previous hexagonal RMnO3 (R =  Y, Ho, Yb) studies. In addition to the resonance effects of the 684 cm−1 mode that are correlated with Mn3+ d–d electronic transitions, some phonon frequencies show anomalous temperature variations suggesting a spin–phonon coupling below TN. The deviation from standard temperature dependence is discussed within a model accounting for the modulation of the exchange interaction by phonon vibrations.

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