Domain walls in single-chain magnets

Abstract

The topology and creation energy of domain walls in different magnetic chains (called Single-Chain Magnets or SCMs) are discussed. As these domain walls, that can be seen as ``defects'', are known to control both static and dynamic properties of these one-dimensional systems, their study and understanding are necessary first steps before a deeper discussion of the SCM properties at finite temperature. The starting point of the paper is the simple regular ferromagnetic chain for which the characteristics of the domain walls are well known. Then two cases will be discussed (i) the ``mixed chains'' in which isotropic and anisotropic classical spins alternate, and (ii) the so-called ``canted chains'' where two different easy axis directions are present. In particular, we show that ``strictly narrow'' domain walls no longer exist in these more complex cases, while a cascade of phase transitions is found for canted chains as the canting angle approaches ${45}^{\ensuremath{\circ}}$. The consequence for thermodynamic properties is briefly discussed in the last part of the paper.