Evidence of Magnetocaloric Effect in (Fe63Ni37)89B11 Nanostructured Magnetic Alloys

Abstract The magnetocaloric effect associated with magnetic entropy changes (Δ S M ) and phase transitions in (Fe 63 Ni 37 ) 89 B 11 (FeNiB) powder alloys was investigated. For this purpose, the particle size of the samples was reduced under milling times of 0 (FNB) and 36 hours (FNB36). X-ray diffraction and Mössbauer spectroscopy results showed the formation of nanostructured magnetic alloys and the coexistence of γ -FCC, α -BCC, and oP-(Fe, Ni)B phases in agreement with the INVAR region. M(H) measurements revealed that both alloys are ferromagnetic soft at room temperature, with coercive field values below ~ 48 Oe. A detailed analysis of the magnetic phase transition using the modified Arrott plot and critical isotherm plots yields critical exponents ( β = 0.27, γ = 0.92, and α = 4.4) close to the theoretical exponents obtained from the Tricritical Mean Field model. Moreover, a maximum magnetic entropy change (Δ S M ) was evidenced around the phase transition ( T C ) at ~ 330 K (− Δ S M of 2.58 J kg −1 K −1 ) for FNB and ~ 415 K ( − Δ S M of 0.4 J kg −1 K −1 ) for FNB36 with an applied field of 1.3 T. The relative cooling power and the temperature-averaged entropy change values were determined, and they exhibited a linear dependency as function of the external field. These findings give a good insight towards the advancements of FNB-based alloys for potential room-temperature magnetic refrigeration technology.