Giant low-field magnetocaloric effect in single-crystalline EuTi_0.85Nb_0.15O₃

Abstract

The magnetocaloric effect in ferromagnetic single crystal EuTi_0.85Nb_0.15O₃ has been investigated using magnetization and heat capacity measurements. EuTi_0.85Nb_0.15O₃ undergoes a continuous ferromagnetic phase transition at TC = 9.5 K due to the long range ordering of magnetic moments of Eu2+ (4f7). With the application of magnetic field, the spin entropy is strongly suppressed and a giant magnetic entropy change is observed near TC. The values of entropy change ΔSm and adiabatic temperature change ΔTad are as high as 51.3 J kg⁻¹ K⁻¹ and 22 K, respectively, for a field change of 0–9 T. The corresponding magnetic heating/cooling capacity is 700 J kg⁻¹. This compound also shows large magnetocaloric effect even at low magnetic fields. In particular, the values of ΔSm reach 14.7 and 23.8 J kg⁻¹ K⁻¹ for field changes of 0–1 T and 0–2 T, respectively. The low-field giant magnetocaloric effect, together with the absence of thermal and field hysteresis makes EuTi_0.85Nb_0.15O₃ a very promising candidate for low temperature magnetic refrigeration.