Magnetic Clusters in the (CuInSe$_2$)$_{1-x}$ (TaSe)$_x$ Alloy System ($0 < x \leq 0.5$)

Polycrystalline samples of (CuInSe$_2$)$_{1-x}$ (TaSe)$_x$ system were prepared by the melt and anneal technique in the composition range $0 < x \leq 0.5$. It was found that the
solubility of TaSe in the CuInSe$_2$ ternary matrix is around \hbox{10 \%}; however, up to $x=0.5$ are composed by a mean tetragonal CuInSe$_2$-like phase with traces of the TaIn$_{0.67}$Se$_2$ phase. A preliminary T-x phase diagram is \hbox{presented. To} determinate the induced magnetic behavior, DC magnetic susceptibility measurements as a function of temperature, using the Zero Field Cooling-Field Cooling (ZFC-FC) protocol, were
performed in samples with compositions $x=0.05$ and $0.5$. It was found that the magnetic behavior evolves from diamagnetic (CuInSe$_2$, $x = 0$) to paramagnetic ($x = 0.05$) to weak ferromagnetic ($x = 0.5$). The observed hysteresis between FC and ZFC curves, for $x=0.05$ and $x=0.5$ suggest the presence of magnetic clusters; fitting FC curves with Langevin function it was found that clusters are composed for approximately $10^3$ Ta-atoms.