Macroscopic behaviour of magnetic shape-memory polycrystals and polymer composites

Single crystals of magnetic shape-memory materials display a large spontaneous deformation in response to an applied magnetic field. In polycrystalline material samples the effect is frequently inhibited by incompatibilities at grain boundaries. This motivates technological interest in textured polycrystals and composites of single-crystal magnetic shape-memory particles embedded in a soft polymer matrix. We use a continuum model based on elasticity and micromagnetism to study the induced macroscopic material behaviour in dependence of such mesoscopic structures via numerical simulation in two dimensions. Our results show that in the case of strong misorientation the spontaneous strain in the composite is significantly larger than in a polycrystal.