Enlarging the magnetocaloric operating window of the Dy2NiMnO6 double perovskite

Abstract

In this paper, we mainly focus on the magnetic and magnetocaloric features of La2-xDyxNiMnO6 double perovskites. Their magnetocaloric properties are investigated in terms of both entropy and adiabatic temperature changes. In contrast to early works, it was found that the Dy2NiMnO6 compound unveils dominant antiferromagnetic interactions under very low magnetic fields. The ordering of its Dy3+ magnetic moments is associated with a giant magnetocaloric effect at very low temperatures, while the established ferromagnetic Ni-O-Mn super-exchange interactions close to 100 K give rise to a moderate magnetocaloric level, only. On the other hand, the doping of Dy2NiMnO6 with high amounts of large-size rare earth elements such as La would enable us to cover an unusually wide magnetocaloric temperature range going from the liquid helium temperature up to room-temperature. More interestingly, the presence of both ordered and disordered ferromagnetic phases in La1.5Dy0.5NiMnO6 maintains constant the isothermal entropy changes over a temperature span of about 200 K, being a favorable situation from a practical point of view.