The behaviour of the elastic constants at the transformation between the modulated phases in Ni2MnGa

The phenomenon of electromagnetic-to-acoustic conversion (EMAC) in modulated parent and low temperature phases in monocrystalline Heusler alloy Ni2MnGa has been investigated. The anomalies in the temperature dependences of EMAC efficiency, low field magnetic susceptibility and velocities of transverse and longitudinal ultrasonic waves both at the Curie point (Tc = 347 K) and the martensitic transformation (Tm = 270 K) from one modulated phase to another are observed. A sharp decrease of the shear modulus c' near Tm has been found.