A ug 2 00 8 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 RAg2Ge2 (R = Pr, Nd and Sm) compounds which crystallize in the ThCr2Si2 type crystal structure with the space group I4/mmm. The single crystals of RAg2Ge2 (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 PrAg2Ge2 and NdAg2Ge2 order antiferromagnetically at 12 K and 2 K respectively, thus corroborating the earlier polycrystalline results. SmAg2Ge2 also orders antiferromagnetically at 9.2 K. The magnetic susceptibility and magnetization show a large anisotropy and the easy axis of magnetization for PrAg2Ge2 and NdAg2Ge2 is along the [100] direction where as it changes to [001] direction for SmAg2Ge2. Two metamagnetic transitions were observed in NdAg2Ge2 at Hm1 = 1.25 T and Hm2 =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.