Generation of Magnetic Noises in Ni2MnGa Single Crystal by Deformation in Martensitic State

In the ferromagnetic Ni₂MnGa material Barkhause-noise can be observed during the magnetization process both in austenitic and martesitic phases. At the martensite-austenite and intermartensitic transformations also magnetic noises are generated without application of external excitation field. From statistical point of wiew these noises can be characterised by power-like distribution functions with different power exponents.

            In martensitic state magnetic shape memory effect can be observed due to the couping of magnetic and martensitic structures. Applying external stress the martensitic variant structure can be easily reoriented. During this process the magnetic domain structure is also changed producing a magnetic noise.

            In present measurements the magnetic noise was generated in martensitic state by low strain rate periodic deformation. The recorded noise was analysed by statistical methods. Distribution functions of noise amplitude, peak width, peak enenergy etc. were studied. The effect of deformation rate, amplitude and external magnetic field was also investigated.