Effects of partial Eu filling in the unfilled skutterudite CoP3

The unfilled skutterudite $\mathrm{Co}{\mathrm{P}}_3$ hosts extremely large magnetoresistance (∼2 × ${10}^4\%$ at 30 T and 2 K), large hole mobility (∼2 × ${10}^4 \mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$, 2 K), and a fourfold quadratic contact point (QCP) above the Fermi level in the electronic structure. We unveil herein that the partial filling of Eu onto the icosahedral void sites of $\mathrm{Co}{\mathrm{P}}_3$ can shift the QCP to lie below the Fermi level while retaining the high carrier mobility (∼1.6 × ${10}^4 \mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$, 2 K). Unlike nonmagnetic $\mathrm{Co}{\mathrm{P}}_3$, partially filled skutterudite ${\mathrm{Eu}}_{0.412}{\mathrm{Co}}_4{\mathrm{P}}_{12}$ is a soft ferromagnet with almost isotropic magnetism. Additionally, an intriguing topological Hall effect is observed, likely hinting an unusual spin texture. In this paper, we provide useful insights into the interplay between magnetism and the nontrivial feature of the electronic band structure, which would guide more efforts in studying this issue.