Anisotropy of the paramagnetic susceptibility in the 3D Dirac semimetal Cd$_3$As$_2$ caused by chromium impurity: the EPR on Cr$^{3+}$ ions

In the literature devoted to magnetic impurities in Dirac semimetals, the appearance of anisotropic and long-range non-oscillating contributions to the Ruderman–Kittel–Kasuya–Yosida interaction is predicted. These contributions are due to the hybridization of the wave functions of magnetic impurities with the wave functions of Dirac electrons, which have a linear dispersion law. We have studied electron paramagnetic resonance (EPR) in powder samples of topological 3D Dirac semimetal Cd$_3$As$_2$ with an admixture of chromium ions. Anisotropy of the magnetic susceptibility in the paramagnetic state was found from the behavior of the resonance field. The appearance of magnetic anisotropy in the paramagnetic state is associated with an increase in the contribution of the orbital moments of chromium ions Cr$^{2+}$ and Cr$^{3+}$ due to their interaction with the orbital moments of donor Dirac electrons, which have anomalously large values of $g$ factors.