Giant magnetocaloric effect in ferromagnetic superconductor RuSr₂GdCu₂O₈

Abstract

We have investigated the magnetic and magnetocaloric properties of ferromagnetic superconductor Ru(Sr_1–xLa_x)₂GdCu₂O₈ (x = 0–0.10) by magnetization and heat capacity measurements. RuSr₂GdCu₂O₈ shows onset of superconductivity at around 46 K, which coexists with the weak ferromagnetic ordering of the RuO2 moments and the antiferromagnetic ordering of the Gd moments. Both superconducting RuSr₂GdCu₂O₈ and non-superconducting Ru(Sr0.9La0.1)2GdCu2O8 compounds exhibit a large magnetic entropy change due to the field-induced metamagnetic transition. The maximum values of entropy change, adiabatic temperature change, and refrigerant capacity are ∼15.5 J kg⁻¹ K⁻¹, ∼14 K, and ∼125 J kg⁻¹, respectively, for a field change of 0–7 T for both the compounds. These magnetocaloric parameters also have reasonably good values for a moderate field change (2–3 T), therefore, fulfilling the necessary conditions for refrigeration in the low-temperature region.