Multiple magnetic phases with tricritical phenomenon in the skyrmion host EuGa2Al2

Abstract

Centrosymmetric skyrmion-hosting materials provide an excellent platform for exploring the interplay between topology and magnetism. Nevertheless, the underlying interaction mechanisms governing their complex phase transitions remain elusive. Here, we systematically investigate the critical behavior and multiple magnetic phases of skyrmion-hosting EuGa 2 Al 2 single crystals. Critical exponents are extracted using modified Arrott plots and Kouvel–Fisher method, yielding β = 0.28 and γ = 0.94 for H / / a b , as well as β = 0.26 and γ = 0.86 for H / / c . These exponents approach the tricritical mean-field model, as further validated by renormalization group analysis. Based on systematic magnetization and scaling analyses, we construct detailed H − T phase diagrams for both crystallographic orientations, which reveal that an external field along the c -axis effectively stabilizes the skyrmion spin texture. Distinct tricritical points are identified at (18 K, 0.2 T) for H / / a b and (18 K, 0.5 T) for H / / c , corresponding to the crossover between first- and second-order phase transitions. Our findings clarify the field-induced anisotropic magnetic configurations and multi-phase evolution in this material, demonstrating that the topological spin textures are stabilized by Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions mediated by itinerant conduction electrons.