Effect of Mn Concentration on Magneto-mechnaical Properties in Directionally Solidified Ferromagnetic Shape Memory Ni-Mn-Ga Alloys.

Heusler type alloys Ni₅₀Mn_25+xGa_25-x (x = 2, 3, 4, and 5) based on near stoichiometric Ni₂MnGa compositions were directionally solidified using modified Bridgman method. The alloys thus prepared were characterised for their chemical composition, crystal structure, microstructure, phase transformation, magnetic and magneto-mechanical properties. The directionally solidified Ni₅₀Mn₃₀Ga₂₀ alloy rod exhibited maximum magnetocrystalline value of 95 kJm^-3 and lowest detwinning stresses for martensite phase of about 5 MPa. The reversible room temperature magnetic field induced strain of 0.2 per cent under external magnetic field of 0.6 T and 0.05 kN bias load was obtained for the directionally solidified Ni₅₀Mn₃₀Ga₂₀ alloy. [ABSTRACT FROM AUTHOR]