Acoustic properties of hematite near the orientation phase transitions in magnetic fields and under pressure

This paper reports on the results of the experimental investigation of the quasi-phonon (quasi-sound) branch of magnetoelastic waves in hematite (α-Fe2O3) in the easy-plane state near the orientation phase transitions in magnetic fields H and under uniaxial pressure P. It has been found that, in an applied external magnetic field H > 1.0 kOe and at a uniaxial pressure P > 40 MPa, the amplitude of the transmitted quasi-sound abruptly increases. The minima of quasi-sound velocities observed at the orientation phase transition points in the magnetic field H are consistent with the predictions of the existing theory of magnetoelastic waves, but their width significantly exceeds the theoretical values. The minima of quasi-sound velocities at a uniaxial pressure P are observed only in magnetic fields H 3 kOe, turn into extended plateaus.