Strain-magnetization property of Ni-Mn-Ga (Co, Cu) microwires

Magnetization associated with reversible phase transformation or rearrangement of martensite variants of two kinds of shape memory alloys under the coupling of tensile stress were investigated. One is the austenitic Ni46Mn28Ga20Co3Cu3 microwire with the [001] preferred orientation, which exhibits enhanced cyclic stability and large fully recoverable strain (> 8%) due to the stress-induced reversible martensitic transformation at room temperature. The other is the Ni54Mn24Ga22 microwire with ferromagnetic martensitic phase, which has preferential orientation and also exhibits large tensile strain. Based on the improved mechanical properties, the strain-magnetization effect of the two kinds of microwire under the coupling of orthogonal magnetic field and tensile stress was performed and the results indicate that the magnetization decreases with the increase of tensile strains. Furthermore, the magnetization mechanism related to the magneto-structural evolution under stress-magnetic coupling was discussed. This study provides a new way for smart magnetic microwires for novel non-contact and non-destructive detection.