The ferromagnetic zircon-type phase of GdCrO4 presents high values for the magnetocaloric (MC) parameters. This compound has large isothermal entropy changes ΔST under the magnetic field action in a wide temperature range, from 5 to 35 K, reaching a maximum |ΔST|=29.0±0.1J/kgK at 22 K, for a field increment ΔB=9 T. It orders ferromagnetically at TC=21.3K via the Cr-Cr exchange interaction and shows a second transition at 4.8 K due to the ordering of the Gd sublattice. The large MC effect is enhanced by the polarization of the Gd3+ ions by the Cr5+ ones via a weaker Gd-Cr interaction. This effect is an interesting feature to be considered in the search for new compounds with a high MC effect in the range of liquid hydrogen or natural gas, regarding the liquefaction of gases by magnetization-demagnetization cycles. This paper contains experimental measurements of magnetization, heat capacity, and direct determinations of the MC effect. The magnetic contribution to the heat capacity Cm has been obtained after subtracting the lattice component. Approximate values for the exchange constants J1 (Cr-Cr) and J3 (Gd-Cr) have been deduced from Cm.

This work has been funded by the Spanish MINECO through Projects No. MAT2013-44063-R and No. MAT2013-44964-R, DGA Consolidated Group E100, and Comunidad de Madrid Project No. S2009/PPQ-1626.

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