Crossover in the Structure Between Bloch and Linear Domain Walls

Abstract

Near the Curie temperature of a ferromagnet the form of a domain wall changes from the Bloch type to (asymptotically) the linear Zhirnov wall. Unlike the simple 180 degree rotation of the magnetization vector in a Bloch wall, its absolute value diminishes near the center of the wall. This leads to a decrease of the total transverse component of the exchange field inside the wall and to an increase of mistracking of the spins of the electrons traversing the wall. This mechanism may help explain large magnetoresistance of domain walls in thin nanowires, as the Curie temperatures of low-dimensional nanostructures are known to be lower than in bulk ferromagnets while the anisotropy energy stays virtually unchanged.