Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Article Title: Attenuating Large Magneto-Entropy, Heat-Capacity And Adiabatic Temperature Change in Heusler Ni41-XMn50Sn9+X<_X1.5) Alloys
by A. A. Prasanna, S. Ram, V. Ganesan and S. Shanmukharao Samantham

Abstract:
A series Ni41-xMn50Sn9+x of Heusler alloys is developed with a partial substitution (x<_1.5) of Ni(4s23d8) by a nonmagnetic Sn(5s24d105p2) in tailoring the martensite <-> austenite transition with functional magnetocaloric properties. It renders composition sensitive magneto-entropy change Sm with an adiabatic temperature change Tad in this transition useful for room temperature applications (x=0.5). The magnetocaloric parameters are estimated from temperature variation of heat-capacity (CP) in a magnetic field (B) and from isothermal magnetization. The B plots give a maximum Sm = 11.8 J/kg-K in a single phase martensite alloy (x = 0) at a magnetic field change ?B = 5 T in the transition at temperature TA =310.5 K. The Sm drops slowly to 11.6 J/kg-K at x = 1.0, or 10.8 J/kg-K at x = 1.5 in a single but austenite phase. In the two phase concur results in an abruptly decreased value 3.3 J/kg-K (x = 0.5). Bit smaller ?Sm by 3-9% appears in a model temperature CP-variation. A large Tad = (-)23.8 K (?B = 5 T) found in a single phase alloy (x -> 0), decreased marginally to (-) 20.7 K by a substitute Sn -> Ni (x = 1.5), values its potential in devising cooling devices

Keywords: heusler alloys, magnetocalory, heat-capacity, magneto-entropy, adiabatic temperature change

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