Influence of lattice expansion on Cr ferromagnetism in Ce (1-x) La (x) CrGe ₃ compounds revealed by atomic-scale measurements

Understanding how lattice effects tune magnetic exchange in intermetallic alloys is essential for controlling functional magnetic properties. Here we investigate Ce (1-x) La (x) CrGe 3 (x = 0, 0.19, 0.43, 0.58, and 1) hexagonal perovskite-type intermetallics using perturbed angular correlation (PAC) spectroscopy combined with structural characterization. La substitution induces a systematic lattice expansion while simultaneously increasing the Curie temperature from 69 K (CeCrGe 3 ) to 84 K (LaCrGe 3 ). PAC measurements using 111 In( 111 Cd) reveal a pronounced increase of the magnetic hyperfine field at the Cr site with increasing La content, despite larger Cr-Cr distances.This counterintuitive behavior suggests a crossover from a relatively itinerant regime in Ce-rich compositions toward a more localized Cr 3d state in La-rich compounds, consistent with lattice-induced band narrowing and modified Cr-Ge-Cr exchange interactions. No magnetic contribution from Ce is detected within experimental sensitivity, confirming that ferromagnetism is governed by the Cr sublattice. These results indicate that lattice expansion is an important parameter for exchange enhancement in RECrGe 3 intermetallic alloys.