Specific heat and magnetocaloric effect in RMnO₃ (R=Gd and Tb) multiferroics

Multiferroic RMnO₃ (R= Gd and Tb) samples were prepared through sol gel method. After characterizing the sample structurally, a systematic investigation of specific heat was performed over the temperature range 4-70 K under 0T, 2T and 5T magnetic fields to study the magnetocaloric effect. The samples are found to exhibit three transitions near 40 K, 25 K and below 10 K. The hump at 10 K broadens under magnetic fields of 2T and 5T, indicating the shift in entropy to higher temperature. The magnetocaloric effect (MCE) of the samples in terms of isothermal entropy change (ΔS) and adiabatic temperature change (ΔT_ad) was evaluated from these specific heat measurements under 2T and 5T magnetic fields. From the systematic analysis it has been observed that the samples can be used as magnetic refrigerant that induces an adiabatic cooling of about ΔT_ad ≈ 2.4 K on application of 5T magnetic fields in the temperature range 4-30 K