Magnetic interactions at Ce impurities in REMn2Ge2 (RE = La, Ce, Pr, Nd) compounds

In the work reported in this paper, the temperature dependence of the magnetic hyperfine field ($B_{h}f$) at ¹⁴⁰Ce nuclei replacing Pr atoms in ${\text{PrMn}}_2{\text{Ge}}_2$ compound was measured by the perturbed angular correlation technique to complete the sequence of measurements in ${\text{REMn}}_2{\text{Ge}}_2$ (RE = La, Ce, Pr, Nd). Results show an anomalous behavior different from the expected Brillouin curve. A model was used to fit the data showing that the Ce impurity contribution ($B_{hf}^{imp}$) to $B_{hf}$ is negative for ${\text{NdMn}}_2{\text{Ge}}_2$ below 210 K. The impurity contribution ($B_{hf}^{imp}$) at 0 K for all compounds is much smaller than that for the free Ce³⁺, showing that the 4f band of Ce is more likely highly hybridized with 5d band of the host. Results show that direction of the localized magnetic moment at Mn atoms strongly affects the exchange interaction at Ce impurities.