Effect of the Landau levels on the super hyperfine structure of ESR spectra of Fe$^{3+}$ precipitates in Dirac 3D semimetal Cd$_{3}$As$_{2}$

The influence of $d$-metal impurities on the magnetic and transport properties of 3D topological semimetal Cd$_{3}$As$_{2}$ has been experimentally studied. It is found that alloying with iron does not change the sign of magnetoresistance (in contrast to Eu). Amplification of oscillations of the parameters (magnetic susceptibility, contact potential difference, and conductivity) related to oscillations of the density of states at the Fermi level is observed with a change in temperature and magnetic field. ESR signals from Fe$^{2+}$ ions (which are most likely the main type of Fe impurity in Cd$_{3}$As$_{2}$) have not been detected in the temperature range of 10–300 K. Weak ESR signals with a super hyperfine structure, which is obviously affected by the Landau levels, have been observed from Fe$^{3+}$ ions.