  Magnetism in Weyl semimetals is desired to investigate the interaction
between the magnetic moments and Weyl fermions, e.g. to explore anomalous
quantum Hall phenomena. Here we demonstrate that proton irradiation is an
effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The
intrinsic magnetism is observed with a transition temperature above room
temperature. The magnetic moments from d states are found to be localized
around Ta atoms. Further, the first-principles calculations indicate that the d
states localized on the nearest-neighbor Ta atoms of As vacancy sites are
responsible for the observed magnetic moments and the long-ranged magnetic
order. The results show the feasibility of inducing ferromagnetism in Weyl
semimetals so that they may facilitate the applications of this material in
spintronics.
