Study of reversible and irreversible magnetization processes using the moving Preisach model

Recent studies of demagnetization processes in permanent magnets have shown that the reversible magnetization can be written as M-rev(H-i,M-irr) where H-i is the internal field and Mi, the irreversible magnetization. The dependence of M-rev on M-irr is given in terms of the so-called inter-relation function eta = (delta M-rev/delta M-irr)H-i. Previous discussion of eta showed that it is possible to find a hysteretic behavior in the reversible magnetization. In the present work, eta is studied using the moving Preisach model, which facilitates a separation of the magnetization into components M-rev and M-irr. In that model, the effective magnetic field acting on the system is H = H-i + k(m) M, where k(m) M is a mean field term associated with the total magnetization M. It is found that the function eta is naturally associated with long range interactions as expressed by the moving parameter k(m), through the relation eta = k(m) chi(rev)(i) Where chi(rev)(i) is the intrinsic reversible susceptibility. Then, for k(m) not equal 0, Mrev is actually hysteretic and eta not equal 0. Also, we show that M-rev is a reversible quantity (non-hysteretic) when considered to be a function of the effective field H = H-i + k(m) M acting on each elementary loop of the Preisach distribution.