| Energy Filtered Lorentz Microscopy (EFLM) combines a high resolution JEOL 4000EX TEM and a post-column Gatan Imaging Filter (GIF), representing a new application for the GIF. An energy filtered magnetic induction mapping technique has been adapted to the EFLM setup. The benefits of zero-loss filtering on both standard and coherent Fresnel and Foucault have been illustrated. It is shown that the signal-to-noise ratio is improved by an order of magnitude for filtered Foucault images. The magnetic resolution of the system is shown to be better than 5 nm for a 7 eV wide slit. Detail on the order of 60 nm has been revealed in induction maps, representing a lower bound on the resolution. The magnetostrictive material Terfenol-D {dollar}rm(Tbsb{lcub}0.73{rcub}Dysb{lcub}0.27{rcub}Fesb{lcub}1.95{rcub}){dollar} has been used to illustrate the various modes of the EFLM, including magnetic induction mapping. A detailed study of micromagnetic configurations in the vicinity of growth twins is presented. Observations compare favorably with micromagnetic models developed by James and Kinderlehrer, confirming that there are indeed two qualitatively different domain configurations possible near twin boundaries. Simulations of Fresnel and Foucault contrast are presented for a particular domain configuration typical to Terfenol-D. The Mansuripur algorithm was implemented for calculation of the Aharonov-Bohm phase shift. Two dimensional periodic boundary conditions for a configuration having an average induction of zero over the unit cell were assumed. An image simulation algorithm which permits direct computation of all stages of the induction mapping process has been implemented to support the observations. Simulated image contrast and reconstructed magnetic induction maps, including domain wall profiles, compare well with the experimentally acquired elastic counterparts. |
