Characterization of nanostructured magnetic alloy based on Ni-Co-Mn produced by mechanical synthesis

Abstract

Nanostructured Ni2MnCo alloy samples were prepared from pure elemental powders by Mechanical Alloying (MA) using a high-energy planetary ball mill. The obtained powders were characterized with XRD, SEM, laser diffraction granulometry and VSM techniques in order to study the microstructural, morphology, particle size distribution and magnetic properties as a function of milling time. The XRD patterns of as-milled powders revealed the formation of the main stage solid solution of Ni2MnCo with fcc structure phase after 24 h of MA. With increasing milling time from 0.5 hr to 50 hr, it is observed that the lattice parameter increases from 3.60 to 3.78 Å as well as an increase of microstrain from 0.17 to 0.41%, whereas the particle and crystallite size decreases down to 3.50 µm and 13 nm respectively. The mixture loses magnetization during the milling process due to the combined effects of crystallites size reduction and the dissolution of the antiferromagnetic compound (Mn) within the host lattice of the alloy. The very low values of the remanence ratio (Mr/Ms) ([1.2E-3, 1.7E-3]), as well as the very low values of the coercive field (≈ 1 Oe), were observed after 16 h of milling, which means that the alloy is magnetically saturated exhibiting a very soft magnetic behavior.