Giant magnetodeformations reachable in ferromagnetic films of Ni_2+x+yMn_1-xGa_1-y Heysler alloy with magnetocontrolled shape memory effect are stimulating their use as components of micromechanical devices (scanning ones, sensor graphic displays, switches, etc.), but until now such explorations are on the initial stage. Differentiated information was received about their synthesis, and only structural magnetic characteristics were measured. Mechanical and acoustical qualities of films are totally unexplored, despite the fact that values of reversible magnetodeformations, elasticity and plasticity are very important characteristics of their practical usage.

Here we consider a Ni₂MnGa (001) film on a (001) susbtrate of a GaAs, Si qubic crystall. In such structure a volumetric ТА₂ with k=[110] satisfies the boundary conditions and is not connected with LA and TA₁. Two last waves are forming Relay wave due to a boundary conditions or a Stounly wave, which are weakly influenced by such phase transition. Axis are to be chosen normally to the film free surface. TA₂ transforms into a Lyav wave in such system. For structures of (001) Ni₂MnGa - (001) GaAs (Si) zero modes of Lyav waves were numerically explored, as most practical and easy-watching ones. It is shown that at their spread along the [110] axis in (001) plane their substantial softening takes place, as far as high sensibility to the film coating thickness and to changes of c`=(c₁₁-c₁₂)/2 elasticity modulus which is responsible for martensite and premartensite phase transitions. Dispersion and frequency dependences are presented for films of 30, 90, and 1000 nm for ferromagnetic, premartensite and martensite stages.

Authors are grateful for BRFFI and RFFI (F04R-080, 04-02-81058, 03-02-17443 grants) for their financial support of carried out researches.

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