Magnetic domain structure in a ferromagnetic shape memory alloy Ni51Fe22Ga27 studied by electron holography and Lorentz microscopy

Behaviors of magnetic domains with cooling in a Ni51Fe22Ga27 ferromagnetic shape memory alloy were examined by electron holography and Lorentz microscopy. A peculiar meshy pattern was observed in the Lorentz microscope image of the parent phase, being concurrent with the anomaly in the thermomagnetization curve. The meshy pattern was found to stem from the heavily bent lines of magnetic flux. The dramatic change in the magnetic domains is presumably due to some intrinsic magnetic instability that is pronounced by cooling, rather than a phenomenon triggered by the lattice modulation as the precursor effect of martensitic transformations or formation of the intermediate phase as observed in other systems. (C) 2003 American Institute of Physics.