Relationship of Microstructure and Magnetic Domain Configuration of a Spinodally Decomposed Cu52Ni34Fe14 Alloy.

Various alloys have shown to be promising materials in terms of manipulating magnetic properties by controlling their microstructure. Despite extensive research activities on such nano-scale magnetic materials for several decades now, the relationship between the evolution of the microstructure and its magnetic properties still remains to be fully explored. [1–4]. In this study, we investigate a spinodally decomposed CuNiFe alloy, using a wide variety of modern (S)TEM methods such as dark-field imaging, 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 [3,5]. EDX elemental maps reveal the characteristic stripe/plate like Ni-rich phase embedded in a Cu-rich matrix [1,2]. 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 which, is similar to the findings of Kobayashi et al [4]. To investigate the magnetic structure, LM-STEM DPC with a switched off objective lens was performed to ensure a nearly field-free environment. In DPC, the deflection of the electron beam due to the interaction with the magnetic field of the specimen is measured with a 4-quadrant annular detector. An in-plane magnetic induction map is shown in figure 1 b), in which the colour represents a certain direction of the magnetic field. The induction map displays a complicated pattern of 90° and 180° domains. Furthermore, these domains exhibit in-plane field vectors not parallel to the [100] directions. Therefore, the DPC findings suggest other directions, such as [111], to be the magnetic easy ones.