Theoretical models of intermediate and inverse AMS fabrics

Abstract

Multi-domain magnetites display a normal anisotropy of magnetic susceptibility (AMS) fabric where grain shape axes coincide with AMS axes. By contrast, single-domain magnetite has an inverse magnetic fabric where magnetic axes are interchanged. The mixing of normal and inverse magnetic fabrics results in intermediate fabrics: Theoretical models for intermediate fabrics consider all combinations of normal and inverse fabrics. The minimum amount of inversé component required for intermediate fabrics to form is about 20% in the case of prolate normal (T = -0.50) and prolate inverse (T = -0.42) components. Such a small amount of inverse component may not be noticed. The anisotropy resulting from intermediate fabrics is lower than that of the normal or inverse contribution to AMS. This suggests that whenever intermediate fabrics occür neither the shape factor nor the degree of anisotropy relate to strain in a simple way.