Magnetic nanostructure of a spinodally decomposed Cu52-Ni34-Fe14 alloy

CuNiFe alloys have shown to be promising materials in terms of manipulating magnetic properties by controlling their microstructure. Despite extensive research activities for several decades now, the relationship between the evolution of the microstructure and its magnetic properties still remains to be fully explored. In this study, we investigate a spinodally decomposed CuNiFe alloy, using modern (S)TEM methods, particularly EDX spectroscopy and differential phase contrast (DPC) imaging. The specimen under investigation was solution treated and a subsequent heat treatment at 625°C for 10 hours leads to a spinodal decomposition of the alloy. EDX elemental maps reveal the characteristic stripe/plate like Ni-rich phase embedded in a Cu-rich matrix. Those plates are growing along the [100] directions of the crystal which is shown in figure 1 a). The EDX analysis reveals a chemical composition of 54 at% Ni, 27 at% Fe and 19 at% Cu for the Ni-rich phase and 15 at% Ni, 4 at% Fe and 81 at% Cu for the Cu-rich matrix. To investigate the magnetic structure, LM-STEM DPC with a switched off objective lens was performed to ensure a nearly field-free environment. A magnetic field map is shown in figure 1 b) in which the colour represents a certain direction of the magnetic field. The DPC map shows a direct relationship between the magnetic field structure and the nanostructure along the [100] directions. Interestingly, the DPC map displays field vectors that point along the diagonals of the image, suggesting a [111] direction of the magnetic easy axis.