SOME NEW ASPECTS OF AN OLD PROBLEM - MAGNETIZATION LAW OF A POLYCRYSTAL

This work is devoted to the study of magnetization processes due to Bloch wall motion in polycrystalline ferromagnets or, more generally, to the evolution of their domain structures. The first part is a review of some results about the behaviour of a single Bloch wall, the statistical features of magnetostatic couplings in a complex domain structure, and the analog simulation of interacting, irreversible events. By combining those different kinds of information, under simplifying assumptions, we study the conditions under which the irreversible motion of a wall remains individual, or in the contrary, trigers an avalanche of jumps of the domain structure. Four differential equations describe the virgin curve and hysteresis loops. The calculated and measured magnetization laws are compared for three differnet samples: hexagonal cobalt, steel, and pure iron. The agreement is quite satisfactory in the ranges of field and magnetization where wall motion is the predominant process.