Contrasting response on magnetocaloric effect and refrigeration capacity due to Ni or Mn substitution by Fe in Ni-Mn-In-Co-Fe alloys

We set the composition of two Ni-Mn-In-Co-Fe alloys as (Ni46.8Fe1.2)Co2Mn36.5In13.5 and Ni48Co2(Mn34.5Fe2)In13.5 in order to display the martensitic transformation near to room temperature. Under a magnetic field change of 5 T the polycrystalline low Co content alloys displayed a large magnetocaloric effect ΔSMag of 15.5 and 20.0 Jkg-1K-1; and giant refrigeration capacity RCFWHM up to 422 and 292 Jkg-1 for (Ni46.8Fe1.2)Co2Mn36.5In13.5 and Ni48Co2(Mn34.5Fe2)In13.5, respectively. The XRD patterns showed cubic L21 structure with space group 225 in both alloys and via Rietveld refinement negligible differences were found in lattice parameter of 0.598(7) and 0.598(9) nm for (Ni46.8Fe1.2)Co2Mn36.5In13.5 and Ni48Co2(Mn34.5Fe2)In13.5, respectively. Nevertheless, the magnetocaloric response in the alloys exhibited remarkable dissimilarities. Whilst the applied magnetic field shifted the martensitic transformation − 3.4 KT-1 in the Ni48Co2(Mn34.5Fe2)In13.5 alloy this sensibility increased up to − 6.8 KT-1 in the (Ni46.8Fe1.2)Co2Mn36.5In13.5 alloy; consequently the span in the Full Width Half Maximum of the ΔSMag(T) curve was 17 and 32 K, respectively.