Magnetic-field-induced strain assisted by tensile stress in L1 martensite of a Ni–Fe–Ga–Co alloy

Abstract

Magnetic-field-induced strains larger than 2% have been obtained in the nonlayered L10 martensite of a Ni49Fe18Ga27Co6 single crystal, under an assisting tensile stress around 16 MPa and fields below 15 kOe. In martensitic samples previously compressed, application of a constant tensile stress along the same axis together with a perpendicular magnetic field produces the elongation of the sample, as one of the variants rotates its c axis from the field direction to the stress-axis direction. An estimated magnetostress of ∼0.8 MPa is in good agreement with the theoretical value given by the ratio of magnetocrystalline anisotropy constant and twinning shear.

Temperature Dependent Stress–Strain Behavior and Martensite Stabilization in Magnetic Shape Memory Ni51.1Fe16.4Ga26.3Co6.2 Single Crystal

“…Among Heusler type FSMAs, the NiFeGaCo alloys represent (to date) the only known analog to classical NiMnGa in terms of a giant MFIS that they show [3,22]. Compared to NiMnGa, these materials are much more ductile (see [23] and references therein) whereby they are much more sustainable to SE cycling, which is an important advantage for their applications in elastocaloric devices [24][25][26].…”

Microstructural and crystallographic characteristics of interpenetrating and non-interpenetrating multiply twinned nanostructure in a Ni–Mn–Ga ferromagnetic shape memory alloy

“…However, Chernenko et al [48] recently observed a MFIS of ∼0.2% in NM martensite, clearly evidencing significant magnetic-field-induced twin boundary motion in NM martensite. Moreover, stress-assisted MFIS has also been successfully achieved in NM martensite [49], [50], [51], making it promising for practical applications. In fact, the NM martensite which is formed as a ground state of the Heusler-type FSMAs [48] has many advantages over 5M and 7M martensites, including high stability, good chemical properties and high ductility [48].…”

Tension/compression asymmetry of functional properties in [001]-oriented ferromagnetic NiFeGaCo single crystals

“…For calculation of the theoretical recoverable strains j3 CVP j and j3 CVPþdtw j, the following lattice parameters were used for the different phases: a 0 ¼ 0.576 (0.288) nm for L2 1 18 for 14M martensite and a ¼ 0.381 nm, c ¼ 0.327 nm for L1 0 -martensite in NiFeGa alloys [2,4]. Recent studies on NieFeeGaeCo alloys have shown that addition of Co to the NieFeeGa system does not significantly change the lattice parameters of austenite and the tetragonal L1 0 -martensite [11,12,15]. For the 14 M structure slightly different lattice parameters of a ¼ 0.420 nm, b ¼ 0.268 nm, c ¼ 2.915 nm, b ¼ 86.3 were determined for a Ni 49 Fe 18 Ga 27 Co 3 (at.%) alloy [16].…”