From nano-dendrite to nano-sphere of Co100−xNix alloy: Composition dependent morphology, structure and magnetic properties

Abstract

Co100−xNix (x = 0, 10, 20, 30, …, 100) alloy nanostructures with controlled composition are prepared by hydrothermal method. The effects of composition on crystal structure, morphology, growth of nanostructure, and magnetic properties are described. The crystal structure is hexagonal closed pack (hcp) at x = 0, mixture of hcp and face-centered cubic (fcc) for 10 ≤ x ≤ 30, and purely fcc for x ≥ 40. The morphology is changed from nano-dendrite (x = 0) to flower like structure composed on spherical core and nanorods (x = 50) to nanosphere (x = 100). The isotropic (spherical shape) character increases with Ni Content. Compositional analyses show the controlled composition in nanostructure. The saturation magnetization is 156 emu/g at x = 0 and decreases linearly with alloy composition (x) to 55 emu/g at x = 100. The coercivity is 285 Oe at x = 0 (dendrite) and decrease gradually to 21 Oe at x = 80, and then increases to 146 Oe at x = 100. The effective anisotropy (Keff) constant decreases gradually with alloy-composition and shows decaying exponential dependence on alloy-composition (x). Magnetic and structural properties are explained by combined consequences of composition and nanoscale effects. This study reveals that the composition of alloy plays important role in growth, morphology, crystal structure and hence, properties of nanostructure.