Transitions from a Kondo-like diamagnetic insulator into a modulated ferromagnetic metal in FeGa<sub>3-y</sub>Ge<sub>y</sub>.

Zhang, Yao; Chen, Jie-Sheng; Ma, Jie; Ni, Jiamin; Imai, Masaki; Michioka, Chishiro; Hadano, Yuta; Avila, Marcos A et al. · Proc Natl Acad Sci U S A · 2018

basic_science · Level V

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Abstract

One initial and essential question of magnetism is whether the magnetic properties of a material are governed by localized moments or itinerant electrons. Here, we expose the case for the weakly ferromagnetic system FeGa<sub>3-<i>y</i></sub> Ge <sub><i>y</i></sub> , wherein these two opposite models are reconciled, such that the magnetic susceptibility is quantitatively explained by taking into account the effects of spin-spin correlation. With the electron doping introduced by Ge substitution, the diamagnetic insulating parent compound FeGa<sub>3</sub> becomes a paramagnetic metal as early as at y=0.01, and turns into a weakly ferromagnetic metal around the quantum critical point <i>y</i>=0.15. Within the ferromagnetic regime of FeGa<sub>3-<i>y</i></sub> Ge <sub><i>y</i></sub> , the magnetic properties are of a weakly itinerant ferromagnetic nature, located in the intermediate regime between the localized and the itinerant dominance. Our analysis implies a potential universality for all itinerant-electron ferromagnets.