Stabilization of various structural phases and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

Abstract

Polycrystalline Co-Ni-Ga ferromagnetic shape memory alloy nanoparticles with phase single austenite (A), martensite (M) and gamma (γ) structures have been obtained for the first time through a facile template-less chemical method. Average crystallite size of A, M and γ phase nanoparticles are 25 nm, 22 nm and 21 nm, respectively. All the synthesized nanoparticles exhibit soft ferromagnetic behavior with saturation magnetization varying from 21.22 to 77.65 emu/g and effective magnetic anisotropy of ∼105 J/m3 at 5 K. Ab initio studies have been performed to evaluate the magnetic moments of single A, M and γ phase. All the single phase nanoparticles have been ascertained to be in single-domain regime by estimating the single-domain size limit. This work showcases a simple methodology to prepare pure crystal phases in these nanoparticles. It also provides insight on the role of elemental precursors and processing conditions in designing Co-Ni-Ga nanoparticles for ferromagnetic shape memory applications.