Positive-Feedback Theory of Hysteretic Recoil Loops in Hard Ferromagnetic Materials

This paper develops a physically-based analytical theory that can be used to model recoil loops, as well as major loops and first- and second-order return curves, in hard ferromagnetic materials that display return-point memory. Atomic-scale quantum-mechanical considerations lead to basic S-shaped magnetization curves that account for hysteretic effects in major and minor loops, as well as their reversibility and irreversibility. These loops exhibit perfect closure only in the presence of the return-point-memory effect. Field (energy) contributions from this hysteretic scenario are summed with contributions due to the classical-physics domain-scale anhysteretic scenario and to the macroscopic demagnetizing field, to obtain a summed scenario that can model isotropic and certain anisotropic materials. Analytical expressions are obtained for all reversal curves up to second order, under the return-point-memory constraint, so that closed recoil loops can be modeled. The theory is validated by comparison with measured data for five different materials.