Soft modes in HoFe2.5Ga0.5(BO3)(4) solid solution

The condensation of two soft modes has been found when studying the Raman spectra of the solid solution HoFe2.5Ga0.5(BO3)4 in the temperature range from 7 to 350 K. The first high-temperature soft mode is associated with the structural phase transition from the R32 phase to the P3121 phase. The second soft mode is related to the reveal of the phonon-magnon interaction during magnetic ordering in the crystal. The temperatures of the structural phase transition T1 ¼ 266 K and the magnetic phase transition T2 ¼ 28 K are established. Experimentally interaction between the structural phase transition order parameter fluctuations and the magnetic order parameter fluctuations was found.