Field-induced Spin Fluctuations in Intermetallic Ce$X_{2}$Ge$_{2 }(X$= Cu, Ag, Au)

Intermetallic rare-earth compounds containing a lattice of 4 $f$ or 5 $f$- electrons are prototypical systems to study the magnetic quantum phase transition which mainly results from the fluctuation of the antiferromagnetic moment at T= 0 K. Therefore, understanding the mechanism behind spin fluctuations is important towards a meaningful universal formulation of the QPT phenomena. We have performed magnetic, thermodynamic and neutron scattering measurements on Ce$X_{2}$Ge2 (X = Cu, Ag, Au) compounds in single crystal form to further understand the mechanism behind spin fluctuations. Ce$X_{2}$Ge$_{2}$ crystallize in a ThCr$_{2}$Si$_{2}$-type tetragonal crystal structure and undergo antiferromagnetic transitions at T$_{N}$ = 4.2 K (Cu), 4.6 K (Ag) and 13.5 K (Au). Detail measurements of Q-vectors associated with the long-range order and the numerical modeling of the data revealed the propagation of amplitude modulated spin density wave in CeCu$_{2}$Ge$_{2}$ and CeAg$_{2}$Ge$_{2}$ with the propagation vectors of (0.29,0.29,0.52) and (0,0.705,0.11) respectively. Dynamic measurements of Ce$X_{2}$Ge$_{2}$ compounds in applied magnetic field, exhibiting the varying nature of spin fluctuations as $X$ changes, will be discussed and compared with other Ce-based intermetallic compounds.