Giant irreversibility of the inverse magnetocaloric effect in the Ni₄₇Mn₄₀Sn_12.5Cu_0.5 Heusler alloy

Direct studies of the adiabatic temperature change (ΔT_ad) in the Ni₄₇Mn₄₀Sn_12.5Cu_0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni₄₇Mn₄₀Sn_12.5Cu_0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature T_C = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔT_ad = -12 K in 20 T at the initial temperature T₀ = 275 K. The irreversible part of the MCE reached ΔT_ir = -10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems.