On the magnetocaloric effect and the spin-phonon coupling in the multiferroic GdMn2O5

The spin-phonon coupling and the magnetocaloric effect (MCE) in polycrystalline GdMn2O5 are investigated by Raman spectroscopy and isothermal magnetization curves. The frequencies of 680 and 700 cm−1 modes show anomalous temperature variations suggesting a strong spin-phonon coupling below the Néel temperature TN ∼ 38 K. The frequency deviation from standard temperature dependence is quantitatively interpreted within a simplified theoretical model accounting for the modulation of the exchange interaction by phonon vibrations. A relatively large magnetic entropy change, ∆Smax = 9.8 J/(kg K), is also achieved with magnetic fields up to 70 kOe. We found that the refrigerant capacity values in GdMn2O5, at different magnetic fields, are quite similar to those of TbMn2O5 and HoMn2O5 in the polycrystalline average approximation. However, the low-cost fabrication of the polycrystalline samples of GdMn2O5 and their large electric polarisation makes this material more suitable for possible cooperative magneto-electrocaloric refrigeration.