Magnetostriction in rare-earth based antiferromagnets

Magnetostriction in systems with rare-earth elements is a very general topic of interest because it characterizes the electronic magnetism of compounds as well as the interaction of the magnetic and the lattice system. The magnetostrictive behaviour of classical ferromagnets is widely investigated. The interpretation of the data is based on domain dynamics, crystal field effects and other magnetoelastic mechanisms, which are extremely difficult to separate. Therefore, in the last few years there has been great activity in the area of magnetostriction of antiferromagnets. In contrast to ferromagnets, in antiferromagnets a large variety of magnetic structures can be stabilized at different temperatures and magnetic fields. This fundamental property of antiferromagnets allows one to separate and distinguish the different mechanisms of magnetostriction. New classes of magnetic compounds with antiferromagnetic order, for example the borocarbides and some special manganites, have also focused research efforts on the magnetostrictive behaviour in order to gain a more complex picture of these materials. In particular, changes of symmetry caused by lattice distortions attracted great interest. Moreover, some antiferromagnetic compounds with giant magnetostrictive effects of more than 1% have been found and the number of publications in this area is growing. The aim of the present review is to summarize experimental data as well as theoretical models concerning spontaneous and forced magnetostriction in antiferromagnetic systems, where the magnetic properties are dominated by the rare-earth magnetism. Above this, the available data, which were acquired with different motivations and therefore are of heterogeneous character, are systematized. After a summary of experimental methods the standard model of rare-earth based magnetostriction is reviewed. Then experimentally determined expansion and magnetostriction data of the pure rare-earth metals are discussed followed by selected rare-earth compounds and giant magnetostriction materials. The potential of a theoretical model which takes into account the crystal field effects as well as the (anisotropic) exchange striction is demonstrated in the interpretation of some of the experimental data.