Study of dual-phase functionalisation of NiCoFeCr-Alx multicomponent alloys for the enhancement of magnetic properties and magneto-caloric effect

Abstract

We have studied the effect of phase separation on the magnetic and magneto-caloric properties of the CoFeNi0.5Cr0.5-Alx (x = 0.0, 1.0 and, 1.5) system. Results show that a collaborative behaviour among FeCr-rich segregated nanoparticles (NPs) increases the saturation magnetisation (Ms) while the Curie temperature (Tc) is controlled by the amount of added Al. With a strong ferromagnetic coupling between segregated FeCr-NPs, the CoFeNi0.5Cr0.5-Al1.0 sample shows the highest Ms (100 Am2 kg−1) with an increase of 61% over the Al-free CoFeNi0.5Cr0.5 sample. It is argued that as the ferromagnetic interaction increases in a degenerated superspin-glass-like state of the NPs the field induced phase transition is broadened while the magnetic entropy decreases. In turn, the CoFeNi0.5Cr0.5-Al1.0 sample shows the highest refrigerant capacity (17.1 J kg−1 at μ0ΔH = 1.0 T), and the smallest measured magnetic entropy change (ΔSmpeak = 0.22 J kg−1 K−1). We found that the enhanced magnetic and refrigerant capacity by mean of phase separation and NPs clustering are among the highest reported for the multicomponent alloys being investigated for energy applications in the high temperature range.