Large reversible magnetocaloric effect in the ferromagnetic pyrochlores R 2Mn2O7 (R = Dy, Ho, Yb)

We report the large reversible magnetocaloric effect (MCE) in the cubic pyrochlores R₂Mn₂O₇ (R = Dy, Ho, Yb) near their second-order ferromagnetic (FM) transition at T_C ≈ 39 K due to a simultaneous FM ordering of rear-earth R³⁺ and transition-metal Mn⁴⁺ localized moments. Under the magnetic field change of 1 T (7 T), the maximum magnetic entropy change −ΔS_M^max is 5.7 (20.1), 4.3 (18.4), 3.9 (13.9) J·kg⁻¹·K⁻¹, and the estimated magnetic refrigerant capacity RC reaches 20.0 (564), 18.4 (503.7), 13.1 (371.4) J·kg⁻¹ for Dy₂Mn₂O₇, Ho₂Mn₂O₇, and Yb₂Mn₂O₇, respectively. We have discussed their magnetic properties and its correlation with MCE in terms of the intrinsic single-ion anisotropy of R³⁺ ions. Our results demonstrate that R₂Mn₂O₇ cubic pyrochlores constitute a promising material platform for magnetic refrigeration applications in the intermediate temperature range.