Crystal Growth and Anisotropic Magnetic Properties of RAg${}_2$Ge${}_2$ (R = Pr, Nd and Sm) Single Crystals

We report the single crystal growth and anisotropic magnetic properties of the tetragonal RAg${}_2$Ge${}_2$ (R = Pr, Nd and Sm) compounds which crystallize in the ThCr${}_2$Si${}_2$ type crystal structure with the space group $\mathit{\text{I4/mmm}}$. The single crystals of RAg${}_2$Ge${}_2$ (R = Pr, Nd and Sm) were grown by self-flux method using Ag:Ge binary alloy as flux. From the magnetic studies on single crystalline samples we have found that PrAg${}_2$Ge${}_2$ and NdAg${}_2$Ge${}_2$ order antiferromagnetically at 12 K and 2 K respectively, thus corroborating the earlier polycrystalline results. SmAg${}_2$Ge${}_2$ also orders antiferromagnetically at 9.2 K. The magnetic susceptibility and magnetization show a large anisotropy and the easy axis of magnetization for PrAg${}_2$Ge${}_2$ and NdAg${}_2$Ge${}_2$ is along the [100] direction where as it changes to [001] direction for SmAg${}_2$Ge${}_2$. Two metamagnetic transitions were observed in NdAg${}_2$Ge${}_2$ at $H_{\mathrm{m}1}$ = 1.25 T and $H_{\mathrm{m}2}$ =3.56 T for the field parallel to [100] direction where as the magnetization along [001] direction was linear indicating the hard axis of magnetization.