Specifics of Determination of Orientation Magnetic Phase Transition Characteristics in Hematite Using Magnetoacoustic Methods

The measurement results of the velocity of magnetoelastic waves in hematite corresponding to their quasi-phonon branch have been presented. The dependences of this velocity ( V ) on the magnetic field ( H ) at constant uniaxial pressure P , ( V P ( H )), and on pressure P at constant H , ( V H ( P )), have been studied. In accordance with the existing theory of magnetoacoustic phenomena, dependences V P ( H ) and V H ( P ) should exhibit minima at the orientation phase transition points. These minima were found, but their coordinates on the plane ( P , H ) did not coincide. The reasons of non-coincidence and requirements to the measurement accuracy are discussed, which yield possibilities of its use to determine characteristics of these transitions.