  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.
