Influence of nickel substitution in an Fe-Sb triangular antiferromagnetic system

Abstract

The iron-antimony system, which occurs in a Ni-As structure, shows interesting magnetic properties and has been investigated by several workers. In order to explore these properties further, we have studied ${({\mathrm{Fe}}_{1\ensuremath{-}y}{\mathrm{Ni}}_{y})}_{1+x}\mathrm{Sb}$ by x-ray diffraction and M\"ossbauer methods in the concentration ranges $0.02\ensuremath{\le}y\ensuremath{\le}0.42$ and $0.08\ensuremath{\le}x\ensuremath{\le}0.16$. Through analysis of the x-ray data, it has been found that these samples are isotypic with ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$, wherein Fe is substituted by Ni, and that the American Society for Testing and Materials data file for ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$ needs modification. Using M\"ossbauer spectroscopic measurements in a transmission geometry at different temperatures, we have determined the N\'eel temperatures, which decrease linearly with increasing $y$. The substitution of Ni atoms in the Fe-Sb lattice produces two new magnetic hyperfine fields which are about 40% and 80% lower than the original field in Fe-Sb. The magnitude of these fields is independent of Ni concentration, whereas the density of sites with these fields increases monotonically with the increase in $y$.