In this letter, we investigated the temperature-dependent Raman spectra of CaMn₇O₁₂ helimagnet from room temperature down to 10 K. The temperature dependence of the Raman mode parameters shows remarkable anomalies for both antiferromagnetic and incommensurate transitions that this compound undergoes at low temperatures. The anomalies observed at the magnetic ordering transition indicate a spin-phonon coupling at higher-temperature magnetic transition in this material, while a magnetostriction effect at the lower-temperature magnetic transition.

Monoclinic BiCrO₃, synthesized at high pressure and high temperature, presents interesting properties with anomalies of magnetic origin observed around 110 and 80 K, which are associated, respectively, with the rise of a G-type antiferromagnetic structure and the spin reorientation along one of the monoclinic axes. In this study, we report a strong spin–phonon coupling in monoclinic BiCrO₃ observed by Raman spectroscopy. The renormalization of the phonon energy confirms the coupling with the magnetic orderings. Interestingly, some phonons exhibit this effect at the rising temperature of the G-type antiferromagnetic ordering, whereas others are sensitive to the second magnetic event. A renormalization model based on the mean-field theory, previously applied to other perovskite compounds, was used to analyze the spin–phonon coupling showing different behaviors associated with each magnetic phase.