de Haas-van Alphen oscillations and anomalous Hall effect in topological nodal line semimetal Ni _0.5 Co _0.5 Se

Here, we present a systematic study of de Haas-van Alphen oscillations (dHvAs), topological phase, and anomalous Hall effect (AHE) of Ni_0.5Co_0.5Se single crystal. Low-temperature longitudinal resistivity<i>ρ</i>_<i>xx</i>(<i>T</i>) under different magnetic fields exhibits an upturn, indicative of a semimetallic phase. Fitting of the zero-field<i>ρ</i>_<i>xx</i>(<i>T</i>) data with the Bloch-Gruneisen-Mott model including Kondo resistivity term reveals multiple scattering mechanisms, which is substantiated by the deviation from Kohler's rule of the magnetoresistance curves. At<i>T</i>= 2 K and low magnetic fields, the observed cusp-like features indicate weak antilocalization effect, quantitatively described using a modified Hikami-Larkin-Nagaoka equation. Temperature dependent magnetization (<i>M</i>-<i>T</i>) curves and magnetic field dependent isothermal magnetization (<i>M</i>-<i>B</i>) curves reveal the existence of weak ferromagnetic phase at very low temperatures. The weak field magnetoconductivity data follows the -ln(<i>B</i>) dependency and the observed strong high field dHvA oscillations in (<i>M</i>-<i>B</i>) curves, provide the evidence of non-zero Berry phase, confirms the non-trivial band topology. These signatures indicate that Ni_0.5Co_0.5Se is a topological nodal line semimetal. In Hall resistivity data, significant AHE is observed at 2 K to 5 K and the linear behavior of the anomalous Hall resistivity (ρxyA) with<i>ρ</i>_<i>xx</i>signifies that the extrinsic skew scattering mechanism contributes to AHE in Ni_0.5Co_0.5Se.