Ultrasonic study of first-order and second-order magnetoelastic properties of yttrium iron garnet

First-order and second-order (in strain) magnetoelastic effects in yttrium iron garnet (YIG) have been studied using a pulsed ultrasonic technique and have been interpreted using finite-deformation magnetoelastic theory. Small-amplitude plane-wave modes in <100>, <110>, and <111> directions in uniformly magnetized, homogeneously deformed cubic single crystals have been analyzed including first-order and second-order magnetoelastic coupling. First-order and second-order magnetoelastic constants have been completely determined for YIG. The second-order "morphic" effect has been analyzed and completely evaluated for YIG in terms of 8 "morphic" constants. Experimental results are described which agree with finite-deformation magnetoelastic theory and disagree with small-strain theory. © 1966 The American Physical Society.