Revisiting, Understanding, and Tailoring the Evolution in the Nature of Phase Transitions in Rare-Earth RE ₂ In Alloys

The nature of magnetic phase transitions, whether first-order (FOMT) or second-order (SOMT), fundamentally impacts material properties. Doping in alloys can alter this nature, but the underlying mechanism remains poorly understood. Here, combining first-principles calculations with Landau–Ginzburg expansion, we investigated the electronic origin of the evolution in the nature of phase transitions in rare-earth RE 2 In alloys. Using Yb-doped Eu 2 In as a test case, we identified that such evolution is governed by the hybridization near the Fermi level between 5 p states of In and 5 d states of the specific Eu site involved in stronger bonding. Furthermore, based on this origin, we clarified the ambiguous “borderline FOMT” in PrNdIn as a weakened FOMT. This understanding enables artificial tailoring of the nature of phase transitions. New materials with targeted phase-transition characteristics can be theoretically predicted and designed prior to experiments by manipulating the hybridization.