“…where T is the undeformed membrane thickness, Ω represents the surface of the undeformed membrane, V 0 the enclosed initial volume and ∆V the change in the enclosed volume, ρ is the mass density, ψ(F, µ) is the free energy per unit mass defined in the formulation based on magnetization (Kankanala and Triantafyllidis, 2004;Barham et al, 2007),P is the gauge pressure of the inflating gas, µ is the material magnetization per unit mass, m = ρµ is the magnetization per unit current volume, µ 0 is the permeability of vacuum, and h a is the applied magnetic field. Note that the formulation here is based on the assumption that the self-generated magnetic field is negligible compared to the applied field.…”