  Spherical nanoparticles (NPs) made of intermetallic Fe2CoAl (FCA) Heusler
alloy are synthesized via the co-precipitation method and its structural,
magnetic and magnetocaloric properties are explored, for the first time. The
basic structural characterizations have revealed A2-disordered cubic Heusler
structure. HRTEM with the SAED pattern analysis revealed the crystalline nature
of the FCA-NPs with a mean diameter of around 14 nm. Field and
temperature-dependent magnetization (M) study show that the NPs are soft
ferromagnetic with a high saturation magnetization (Ms) and Curie temperature
(Tc). We also observed that FCA-NPs do not follow the Slater Pauling (SP) rule
possibly because of the disorder present in this system. We further investigate
its phase transition and magnetocaloric properties. The peak value of magnetic
entropy cange vs T curve at a magnetic field change of 20 kOe corresponds to
about 2.65 J/Kg-K, and the observed value of refrigeration capacity (RCP) was
as large as 44 J/Kg, suggesting a large heat conversion in the magnetic
refrigeration cycle. To analyze the magnetic phase transition (MPT), the
magnetization property is studied in detail. The Arrott plot and the nature of
the universal curve accomplish that the ferromagnetic (FM) to paramagnetic (PM)
phase transition in FCA-NPs is of second order. The present study suggests that
the Fe2CoAl nanoscale system is proficient/useful/a good candidate for the
spintronics application and opens a window for further research on full-Heusler
based magnetic refrigerants.
