Modelling magnetostructural textures in magnetic shape-memory alloys: Strain and magnetic glass behaviour

• Published in: Physica Status Solidi. B: Basic Solid State Physics Vol. 251; no. 10; pp. 2080 - 2087
• Main Authors: Lloveras, Pol, Touchagues, Gilles, Castán, Teresa, Lookman, Turab, Porta, Marcel, Saxena, Avadh, Planes, Antoni
• Format: Journal Article Publication
• Language: English
• Published: Blackwell Publishing Ltd 01-10-2014
• Subjects: Anisotropy; Energies; Enginyeria dels materials; Free energy; Glass; Magnetic glass; Magnetic materials; Magnetic shape memory; Magnetism; Magnetisme; Magnetization; Martensitic transition; Materials funcionals; Materials magnètics; Mathematical models; Shape memory; Strain; Strain glass; Texture; Àrees temàtiques de la UPC
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201350394

In this paper, we propose a model that combines a Landau free energy part and a micromagnetic free energy part aimed at describing a magnetostructural multiferroic. We show that in the limit of high‐elastic anisotropy and strong magnetostructural interplay, the model is able to reproduce characteristic strain and magnetization configurations typical of magnetic shape‐memory materials. For low‐elastic anisotropy, in the presence of disorder arising from compositional fluctuations giving rise to a distribution of local transition temperatures, the model is able to reproduce strain glass behaviour. In this case, the temperature dependence of the magnetization measured after zero magnetic field cooling deviates from the magnetization measured after magnetic field cooling protocol, which proves that the strain glass behaviour induces non‐ergodicity in the magnetic degrees of freedom as well.
Lloveras et al. study a model for systems undergoing a magnetostructural transition that combines a Ginzburg–Landau free energy accounting for the structural contribution together with a micromagnetic term that describes the magnetic and magnetostructural contributions. Both strain and magnetic glass behaviour is predicted to occur in off‐stoichiometric magnetic shape‐memory materials with
low elastic anisotropy.