Synthesis and Characterization of Single Phase γ-Co46–x Ni22+x Al32 (x = 0, 10, 20) Heusler Alloy Nanoparticles

Off-stoichiometric single phase $\gamma $ -Co46Ni22Al32, $\gamma $ -Co36Ni32Al32, and $\gamma $ -Co26Ni42Al32 nanoparticles have been synthesized for the first time by a facile template-less chemical method with the average crystallite sizes of 34 ± 1, 34 ± 1, and 30 ± 1 nm, respectively. Obtaining the high-purity secondary $\gamma $ phase in the nanometer regime with particle sizes of 68, 48, and 57 nm is the first step in developing Co-Ni-Al shape memory alloys in low dimensional form. Co46Ni22Al32, Co36Ni32Al32, and Co26Ni42Al32 nanoparticles exhibited soft ferromagnetic behavior with very high magnetic moments of 3.1, 2.8, and 2.2 $\mu _{\mathrm {B}}$ /f.u. at 5 K and 3.0, 2.8, and 2.1 $\mu _{\mathrm {B}}$ /f.u. at 300 K, respectively. These nanoparticles are suited for fabricating high-temperature nanoscale magnetic devices since they exhibit a reasonably effective anisotropy constant of ~105J/m3 and Curie temperature (988–1164 K) apart from their role in enhancing of ductility of the martensite and austenite phases of shape memory alloy.