Magnetic domain pattern in hierarchically twinned epitaxial Ni-Mn-Ga films

Magnetic shape memory alloys exhibit a hierarchically twinned microstructure, which has been well examined in epitaxial Ni-Mn-Ga films. Here we analyze consequences of this twin within twins microstructure on the magnetic domain pattern. Atomic and magnetic force microscopy are used to probe the correlation between the martensitic microstructure and magnetic domains. We examine consequences of different twin boundary orientations with respect to the substrate normal as well as variant boundaries between differently aligned twinned laminates. A detailed micromagnetic analysis is given which describes the influence of the finite film thickness on the formation of magnetic band domains in these multiferroic materials.