Recent breakthrough development of the magnetic shape memory effect in Ni–Mn–Ga alloys

Abstract

Magnetic shape memory (MSM) alloys or ferromagnetic shape memory alloy (FSMA) materials discovered by Ullakko et al (1996 Appl. Phys. Lett. 69 1966 have received increasing interest, since they can produce a large strain with rather high frequencies without a change in the external temperature. These materials have potential for actuator and sensor applications. MSM materials exhibit giant magnetic field induced strain (MFIS) based on the rearrangements of the crystallographic domains (twin variants). The magnetization energy of the material is lowered when such twin variants that have the easy axis of magnetization along the field start to grow due to twin boundary motion. Currently, the best working MSM materials are the near-stoichiometric Ni 2 MnGa Heusler alloys in which the properties are highly composition dependent. Their modulated martensitic structures, 5M and 7M, show 6% or 10% response respectively in a magnetic field less than 800 kA m −1 . The MSM service temperature of the 5M alloys is between 150 and 333 K, and the optimal frequency region is up to 500 Hz. The fatigue life of the MSM elements has been shown to be at least 50 × 10 6 shape change cycles. This paper reviews the research work carried out at

Local atomic arrangement and martensitic transformation in Ni50Mn35In15: an EXAFS study

“…These materials also offer an excellent opportunity to investigate the various aspects of magnetic and structural phase transformations in a single system [3,4]. As a magnetic field controlled shape memory effect is realized in these materials upon martensitic transformation, they are commonly reffered to as "ferromagnetic shape memory alloys" or FSMA.…”

Tailoring superelasticity of soft magnetic materials

“…Both mechanisms are stress-induced and rea) Electronic mail: pcremer@thphy.uni-duesseldorf.de b) Electronic mail: menzel@thphy.uni-duesseldorf.de spond to external magnetic fields. Therefore, superelasticity can be switched on and off, and also its magnitude and position on the stress-strain curve can be reversibly tailored during operation, as has been realized for some special metallic components 32,33 . The superelastic behavior in our case covers a significantly larger strain regime.…”

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

“…Ferromagnetic shape memory alloys (FMSAs) are relatively new class of active materials exhibiting large strains (up to 10 per cent) under an external magnetic field [1][2][3][4][5] . The phenomenon of ferromagnetic shape memory (FMSM) is explained on the basis that twin variants of the martensitic phase are reoriented by the application of magnetic field [6][7][8][9][10] .…”