|Conditions are examined of generation, spread and registration of Rayleigh surface acoustic waves (SAW) on a massive substrate of the high Q-factor acoustic crystal, covered with a thin film of the Heysler ferromagnetic alloy with shape memory and combined magneto-structural phase transition (PT) – Ni53Mn25Ga22, Ni2.18Mn0.82Ga and Ni2.14Mn0.81Fe0.05Ga with PT at room temperature. SAW are generated and received by interlocking-finger transducer (IFT), mounted on the yz-cut of lithium niobate Li2O3. 350 mm plates of Si covered with thin 5 μm Ni-Mn-Ga film coating, both of (100) orientation, are placed on these IFT. So experiments were carried out along with the bridge circuit. A 35 Mhz sensor was in the positive frequency feedback with the main high stable oscillator. Placing ferromagnetic film on the silicon substrate substantially increases the selectivity, resolution and sensitivity of thew sensor to hydrocarbons concentration in the air. The amount of admixtures in the air was registered on frequency shift of the setting generator and is about 1 ppm/sm2.
Chemical substances sensible to some of the gas mixture components been placed on the sensor surface provide a sort of the 'electronic nose' device. Such devices based on chemical sensors are intended to substitute taste and smell receptors of humans. Electronic nose can be successfully used to control the air quality, gas and liquid wastes of industry and agriculture, and for other ecological tasks. Other usage area includes earlier fire alarm systems, determining the volatile burning products, and systems of automated manufacture safety control.