The Hunting of the Psark

Abstract

At least four types of sub-domain magnetic moments, on a scale smaller than the main domain structure, could contribute to pseudo-single-domain intensities of TRM (thermoremanent magnetization) in small multidomain grains. Of these, moments pinned by the stress fields of dislocations, surface moments, and moments due to the Barkhausen discreteness of domain wall positions are either strongly shielded by the magnetically soft matrix, subject to the internal demagnetizing field during magnetization changes, or so coupled to the domain structure that they cannot change magnetization independently. Only the net moments of domain walls themselves qualify as psarks'-subdomain moments with truly single-domain behaviour. A new reversal mode, domain wall inversion or curling, is postulated to explain the incoherent reversal of domain wall moments. It amounts to nucleating and propagating a Bloch line across a 180°C domain wall. © 1977, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.