1.1.7 Magnetoelastic interactions

Ferromagnetic bodies are also sensible to mechanical stress and deformations. This means that when they are subject to an external field, mechanical stresses, due to the interaction with the field, arise within the bodies and consequent deformations of the bodies themselves can be observed (magnetostrictive materials). Viceversa, if one deforms a ferromagnetic body, the consequent mechanical stress affects the state of magnetization of the body. In other words, there is interaction between magnetic and elastic processes. Therefore, in our framework based on energy aspects, an additional term to describe this magneto-mechanical coupling should be inserted in the free energy (see Ref. [19] for details). Here we neglect magnetoelastic interaction, for sake of simplicity, but in principle it can be treated, apart from mathematical complications, in the same way as the other free energy terms, as we will see in the following sections.