First principles approach to magnetostrictive hysteresis (abstract)

A theoretical result for the magnetostriction λ in a ferromagnet is obtained via minimization of the energy with respect to the strains. This result contains terms which produce three experimentally observed hysteretic phenomena which hitherto have not been explained by existing models.1 The first of these phenomena is liftoff. Although the magnetostriction starts at zero in the unmagnetized sample, it never returns to zero as the external magnetic field H is cycled around the magnetostrictive hysteresis loop. This liftoff phenomenon is seen experimentally in iron.1 Second, the butterfly-shaped hysteretic variation of magnetostriction against magnetic flux density B now exhibits a negative derivative ∂λ/∂B just as the flux density decreases from its maximum in agreement with experiment. Thirdly, the λ-vs-H loops are in general wider loops than the λ-vs-B loops, which is quite noticeable experimentally in iron.1 Thus, our new result exhibits all the characteristics of experimentally observed magnetostriction hysteresis.