Effect of Dy substitution in the giant magnetocaloric properties of HoB₂

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB₂. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho_1- Dy B₂ alloys (x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature (T _C) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |ΔS _M| and adiabatic temperature change ΔT _ad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10-60 K.