Dynamic control of elasticity by means of ultrasound excitation in antiferromagnets

Abstract

Sound velocity control by resonance ultrasonic oscillations in a magnetoordered medium is demonstrated experimentally on a sample of α-Fe 2O 3 single crystal. The phenomenon is caused by giant nonlinearity introduced by the crystal magnetic subsystem into the elastic one. The sensitivity of the dynamic elasticity control obtained in the experiment is ( Δν/ν)/a 2 p =10 −5 ppm −2 , where Δ ν is the variation of sound velocity under an ultrasonic deformation of the amplitude a p. From another side, the acoustically induced static deformation caused by the magnetoelastic nonlinearity is estimated, for the same experimental conditions, as 0.64 ppm when an alternative deformation of amplitude a p=20 ppm is applied. As it is shown both values are coupled in agreement with the theory.