A New Kind of Functional Crystal Ni_2MnGa

Ni2MnGa crystal is a new kind of functional material, which exhibits ferromagnetic, magnetostrictive, thermal and magnetically controlled shape memory properties. The nonstoichiometric Ni2MnGa crystal can show a strain of 0.31% along [001] direction in a magnetic field of 6kOe at room temperature; a [001]-directed stress of only 2MPa gives rise to a recoverable strain of 5%. As a kind of future actuator and sensor material, it will possibly be used in many fields, such as sonar, microactuator, linear motor, microwave device, vibration and noise control, robot and functional structure etc. This paper presents the properties of Ni2MnGa crystal, the essential and mechanism of the magnetic-induced martensitic transformation and magnetically controlled shape memory effect. Some factors which may influence the properties of Ni2MnGa are also discussed.