Transmission electron microscopy/electron energy loss spectroscopy measurements and ab initio calculation of local magnetic moments at nickel grain boundaries

摘要

We have determined local magnetic moments at nickel grain boundaries using a transmission electron microscopy/electron energy loss spectroscopy method assuming that the magnetic moment of Ni atoms is a linear function of the L3/L2 (white-line ratio) in the energy loss spectrum. The average magnetic moment measured in the grain interior was 0.55 μB, which agrees well with the calculated magnetic moment of pure nickel (0.62 μB). The local magnetic moments at the grain boundaries increased up to approximately 1.0 μB as the mis-orientation angle increased, and showed a maximum around 50°. The respective enhancement of local magnetic moments at the Σ5 (0.63 μB) and random (0.90 μB) grain boundaries in pure nickel was approximately 14 and 64% of the grain interior. In contrast, the average local magnetic moment at the (111) Σ3 grain boundary was found to be 0.55 μB and almost the same as that of the grain interior. These results are in good agreement with available ab initio calculations.