Synthesis and magnetocaloric characterization of rapidly solidified ErMn2 melt-spun ribbons

Abstract

We have fabricated melt-spun ribbons of nominal composition ErMn2 and studied their phase constitution and magnetocaloric (MC) properties by X-ray diffraction, scanning electron microscopy (SEM), magnetization and heat capacity measurements. The major phase formed shows the MgZn2-type hexagonal structure (C14-type); however, both XRD and SEM analyses revealed the formation of impurity phases (i.e., Er6Mn23 and ErMn12). Ribbons exhibit a saturation magnetization of 149 Am2kg−1 at 2 K and a Curie temperature of TC = 15 K. A field-induced metamagnetic transition at very low critical magnetic fields was observed below 8 K that leads to a change of sign in the magnetic entropy change ΔSM below this temperature (ΔSMpeak = 2.5 Jkg−1K−1 at 2 K and 5 T). For a magnetic field change of 5 T (2 T) applied along the ribbon length, the samples show a large peak value of the magnetic entropy change ΔSMpeak of −20.5 (−10.8) Jkg−1K−1, a full-width at half-maximum δTFWHM for the ΔSM(T) curve of 20 (12) K, and a maximum adiabatic temperature change ΔTadmax of 7.4 (3.6) K. The obtained results are compared with the reported in literature by other authors for bulk alloys.