Determination of the elastic limit in ferromagnetic materials using the mechanical barkhausen effect

Magnetomechanical Properties of the Alloy Nd2Fe14B

“…(2), is called magnetoelastic saturation. In ferromagnets, the thickness δ of the boundary layer between domains is determined by the equilibrium between exchange and anisotropy forces [14], and in a real uniaxial ferromagnet is…”

“…A size effect is connected with the existence of a transitional layer between domains: a Barkhausen jump occurs on an internal defect with a size on the order of the width of the interdomain boundary δ. Consequently[14], during deformation the number of Barkhausen jumps will be proportional to the number of defects of size on the order of δ.Becauseof the huge positive value of the first-order anisotropy constant in Nd 2 Fe 14 B, K 1 = 4.2 ⋅ 10 6 J/m 3 (for comparison, in iron K 1 = 4.2 ⋅ 10 4 J/m 3 ), the width of the boundaries between domains is extremely small: δ ≈ 0.004 µm (in α-iron, δ ≈ 0.1 µm). Magnetooptic studies showed that there are no defects inside grains of Nd 2 Fe 14 B, and therefore displacement of domain boundaries can be impeded only on intergrain segregations or grain boundaries…”