Polycrystalline samples of lightly doped manganite La1–xCaxMn0.98Fe0.02O3+δ (x = 0.05, 0.1, 0.2) were studied by Raman scattering. With increasing calcium content, the optical LO phonon bands, expressed only in samples of stoichiometric composition (δ = 0, rhombic phase), are significantly weakened and broadened. In individual crystallites (~20%) of the sample with x = 0.05, the temperature dependences of the phonon ν ≈ 610 cm–1, corresponding to symmetrical stretching of the MnO6 octahedra, show softening below the magnetic ordering temperature T ≈ 120 K. This indicates a strong coupling of the magnetic and phonon systems, as well as significant heterogeneity of the lightly doped samples.
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Zaitsev et al. (2026) studied this question.
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