Review of Magnetoacoustic Residual Stress Measurement Technique for Iron-Like Ferromagnetic Alloys

The stress dependence of the magnetoacoustic response in ferromagnets is based on two distinct, but not mutually independent, phenomena: stress dependence of domain structure and domain structure dependence of elastic modulus [1,2,3]. A difference in magnetoelastic energy density exists between two neighboring domains unless α, the angle between the uniaxial stress axis and magnetization vector, is the same for both domains. This difference is a net pressure acting on domain walls and, apparently, is non-zero only for 90° domain walls as long as α is different from 45° [4]. Application of uniaxial stress, hence, induces motion of 90° domain walls such that domains in iron-like ferromagnets align parallel (perpendicular) to the uniaxial tensile (compressive) stress axis. Producing local 90° domain wall motions, the same trend is valid for a stress wave propagating in these materials