Study of magneto-structural phase transitions and magnetocaloric effects in Co-based Heusler alloys synthesized via mechanical milling

In the present study, the effect of complete replacement of Cr by Fe dramatically enhances the structural, magnetic and magnetocaloric effect (MCE) of Co2(Cr1−xFex)Al (x = 0 and 1) Heusler alloys was studied. The present Heusler alloy systems were successfully prepared by mechanical alloying via high energy ball milling technique. Evolution of the B2 type disordered phase along with A2 type structure has been observed through X-ray diffraction. The substitution of Fe would lead to the development of remarkable enhancement of MCE observed near room temperature. The magnetic entropy (ΔSM) values of 10.77 J/kg-K and 17.46 J/kg-K, and refrigerant capacity (RC) 136.31 mJ/cm3 and 30.30 mJ/cm3 respectively are observed under an applied field of 20 kOe. The increment in magnetic entropy and refrigeration capacity with increasing Fe was associated with variation in lattice defects, and the presence of small amounts of magnetic/nonmagnetic secondary phases. Therefore, the increment in magnetic properties of these alloys was attributed to the enhancement of d-d exchange interaction due to the possible occupancy of vacant sites by Fe atoms, which indicates the development of relative anisotropy.