Resistive and low-temperature magnetoresistive properties of pressed powders of ferromagnetic halfmetal chromium dioxide (CrO₂) with shape anisotropy of nanoparticles are studied. And we also studied the influence of Fe impurity on the value of tunneling resistance and magnetoresistance in CrO₂ powders. It is found that the Fe impurity reduces resistance and tunneling magnetoresistance in chromium dioxide. We suggest that such a decrease of magnetoresistance in solid solution Cr_1-xFe_xO₂ is due to the formation of additional localized states at the iron impurities in a tunnel barrier. We found the influence of the speed of the magnetic field changing on the form of lowtemperature tunneling magnetoresistance hysteretic loops in Cr_1-xFe_xO powder. It is shown that the form of low-temperature magnetoresistance hysteresis depends on the relaxation rate of the magnetic moments of nanoparticles to an equilibrium state. The possible reasons for such dependence are discussed. PACS: 75.47.-m Magnetotransport phenomena; materials for magnetotransport; 75.47.Lx Magnetic oxides; 75.50.Ss Magnetic recording materials; 72.25.-b Spin polarized transport.