Modeling the interrelating effects of plastic deformation and stress on magnetic properties of materials

A model has been developed that describes the interrelating effects of plastic deformation and applied stress on hysteresis loops based on the theory of ferromagnetic hysteresis. In the current model the strength of pinning sites for domain walls is characterized by the pinning coefficient k(eff) given by k(eff)=k(0)+k'sigma. The term k(0) depicts pinning of domain walls by dislocations and is proportional to rho(n), where rho is the number density of dislocation which is related to the amount of plastic strain, and the exponent n depends on the strength of pinning sites. The second term k'sigmaproportional to-3/2lambda(s)/2msigma, where m is magnetization and lambda(s) is magnetostriction constant, describes the changes in pinning strength on a domain wall induced by an applied stress sigma. The model was capable of reproducing the stress dependence of hysteresis loop properties such as coercivity and remanence of a series of nickel samples which were pre-strained to various plastic strain levels. An empirical relation was found between the parameter k(0) and the plastic strain, which can be interpreted in terms of the effects on the strength of domain wall pinning of changes in dislocation density and substructure under plastic deformation. (C) 2003 American Institute of Physics.