Magnetic and Fermi Surface Properties of Semimetals EuAs₃ and Eu(As_1−xP_x)₃

A Eu-divalent antiferromagnet EuAs3 exhibits six magnetic phases in the magnetic field vs temperature (H-T) phase diagram for the magnetic field along the monoclinic b*(b)-axis. The existence of such multiple magnetic phases is rare among Eu compounds because the magnetism is governed by the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction and the corresponding localized 4f-electrons only exhibit the spin angular momentum S. To clarify characteristics in these magnetic phases of EuAs3 and Eu(As1-xPx)(3) (0.7 < x < 0.97), we measured the magnetization, magnetoresistance, and Hall resistivity using single-crystal samples. A large anomalous Hall resistivity was found in these magnetic phases, especially in Eu(As0.97P0.03)(3). In addition, we carried out de Haas-van Alphen (dHvA) experiments to clarify the Fermi surface properties of the semimetal EuAs3, and it was revealed that there are small and closed electron and hole Fermi surfaces with equal volumes.