Microstructural evolution and correlated magnetic domain configuration of nanoparticles embedded in a single crystal of Cu75–Ni20–Fe5 alloy

Abstract

We have investigated the microstructural evolution and magnetic domain configurations in nano-scale Fe–Ni rich precipitates formed in a single-crystal specimen of Cu–20at%Ni–5at%Fe alloy on isothermal annealing at 873 K and 973 K, using a combination of transmission electron microscopy (TEM), electron backscattering diffraction, field-emission scanning electron microscopy (FE-SEM), and laser-based photoemission electron microscopy (laser-PEEM). The TEM and FE-SEM observations showed that small, spherical solute-rich particles formed randomly in the initial stage of the precipitation, but on isothermal annealing, cubic, rectangular, plate-shaped and rod-shaped precipitates appeared and aligned along the <1 0 0 > directions in the copper-rich matrix. Laser-PEEM was applied to single-crystal specimens of the alloy and allowed direct observations of magnetic domain configurations in individual ferromagnetic particles at the nanometer scale. This revealed that cubic particles of size approximately 50–60 nm consist of single magnetic domains, but particles of size 100 nm have a closed spin structure (e.g. vortex or multiple domains).