Analysis on magnetocaloric and structural properties of heusler alloys used in magnetic refrigeration

The prime importance of the majority of the research works being undertaken in the field of magnetic refrigeration is, to achieve the refrigeration at or near the room temperature in heusler alloys. The current review work surveys the magnetocaloric effects, range of temperature where the phase transformation occurs in heusler alloys and discusses their relation with the magnetic shape-memory and structural variation of the materials in accordance to the variation in its material composition. The e/a ratio of the material are considered to predict the composition of the refrigerant alloy. System having a near room temperature martensitic transformation and various compositional changes done to achieve the same are discussed thoroughly. Substitutions of constituent elements are done such that a favorable magnetic entropy change is retained and the formulation of near room temperature martensitic transformation of the alloy is formed. Around 100 existing research articles are studied to collect the information on above said parameters and displayed in a collective form in this systemic review. The review reveals that, as on date, the properties examined are martensitic transformation temperature, magnetocaloric value and structural properties. Ni₄₅Mn_36.5In_13.5Co₅ alloys show a martensitic transformation temperature of 294 K, which is equivalent to near room temperature; hence these can be used as a refrigerant material in conventional refrigerator system. Change in entropy at x= 4, 5 is 43 and 68 J/kg K for Ni₅₀−xCo_xMn₃₈Sb₁₂ alloy was observed for all the works considered for x varying from 0–7.