Influence of the lattice discreteness on magnetic ordering in nanostructures and nanoarrays

The article attempts to analyze the effect of lattice discreteness on the magnetic ordering in nanostructures and nanoarrays. The discussion starts with a basic introduction of the theoretical methods for the description of the magnetic ordering. Next it is shown that the discrete nature of an atomic lattice may lead to the size-driven reorientation of magnetization in nanoparticles, i.e., the magnetization direction can be changed by shrinking the lateral size, keeping the thickness fixed. It is demonstrated that in finite nanomagnets the shape anisotropy can be divided into the discrete and continuum contributions. Then the orientation of magnetic domain walls in low-symmetry objects is discussed. It is shown theoretically that in nanomagnets of monolayer thickness the mechanism of the orientation of domain walls is different from that of bulk systems and is mainly determined by the discreteness of the atomic lattice and the exchange energy. In the last part the theoretical study of magnetostatically interacting nanoarrays is presented. Special attention is paid to the influence of the underlaying lattice symmetry and the higher order multipolar terms on the magnetic ordering. It is demonstrated that the multipole-multipole interactions lead to an enhancement/decrease of the coercivity in arrays with in-plane/out-of-plane magnetization, respectively. In each section of the manuscript the agreement between the theory and recent experimental results is analyzed. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.