The effect of stress on the susceptibility and magnetization of a partially magnetized multidomain system

Abstract

An analysis of the effects of directed stress on magnetization and susceptibility is presented, with special attention to the problems of rock magnetism. A model is proposed for partial magnetization of an isotropic multidomain magnetic system. The behavior of the model system in response to applied stress is analyzed. It is found that the response of the system to applied stress, given by the ratios of magnetization and susceptibility to their respective initial values, is simply related to the saturation magnetization and magnetostriction parameters for the system and to the initial susceptibility. The behavior of these two ratios is approximately the same. This behavior can be approximated very closely by the function a/(S+a), where a is defined as the ‘Virtual initial stress’ and S is the normal deviatoric component of the applied stress. The value of a is given by J2/3λx0, where J is the saturation magnetization, λ the saturation magnetostriction, and X0 the initial susceptibility. The theoretical results are compared with isothermal experiments by Grabovsky and Parkhomenko for magnetite and titanomagnetite, and the agreement is found to be quite good. The virtual initial stress parameter can be calculated for high temperatures using Kneller's experimental data for nickel. The conclusion is drawn that the stress response is regular with temperature, and it has no strong effects even where the magnetization vanishes at the Curie point.