Linear arrangements of nano-scale ferromagnetic particles spontaneously formed in a copper-base Cu–Ni–Co alloy

Abstract

We have investigated the influence of magnetic interactions on the microstructural evolution of nano-scale granular precipitates formed spontaneously in an annealed Cu-20at%Ni-5at%Co alloy and the associated changes of magnetic properties. The techniques used included transmission electron microscopy, superconducting quantum interference device (SQUID) magnetometry, magneto-thermogravimetry (MTG), and first-principles calculations based on the method of Koster–Korringa–Rostker with the coherent potential approximation. Our work has revealed that the nano-scale spherical and cubic precipitates which formed on annealing at 873 K and 973 K comprise mainly cobalt and nickel with a small amount of copper, and are arranged in the 〈1 0 0〉 direction of the copper matrix. The SQUID and MTG measurements suggest that magnetic properties such as coercivity and Curie temperature are closely correlated with the microstructure. The combination of results suggests that magnetic interactions between precipitates during annealing can explain consistently the observed precipitation phenomena.

Spontaneous Microstructural Evolution and Magnetic Properties of Nano-Scale Particles Comprising Ferromagnetic Element Atoms in Cu-Ni-Fe and Cu-Ni-Co Alloys

“…We interpreted this distinctive feature based on the influence of magnetic interaction between particles. Further studies have successfully obtained the results supporting the interpretation to the feature, using PEEM [6] and magneto-thermogravimetry [7]. The present study aimed to examine the influence of element and composition on microstructure magnetic properties in Cu-based nano-granular magnetic materials.…”

“…Recently, our group reported a characteristic microstructure in which nano-scale magnetic particles are arranged in the <100> direction of the copper matrix in Cu-Ni-Fe and Cu-Ni-Co alloys [6][7][8]. We interpreted this distinctive feature based on the influence of magnetic interaction between particles.…”

“…Electron Energy band structures of precipitates and matrices TEM observations revealed that distinctive microstructures formed in Cu-Ni-Fe and Cu-Ni-Co alloys during annealing. The microstructures suggest that magnetic interaction may give an influence on the phase separation as seen in Cu 75 -Ni 20 -Co 5 alloys [7]. Nevertheless, few studies have explored the phenomena from this viewpoint so far.…”