The effect iron impurities have on the low-temperature behavior of the magnetoresistance of compacted powders of CrO₂ ferromagnetic half-metal with anisotropic particle shape is investigated. The strong dependence of magnetoresistance on the spin relaxation rate during specimen magnetization reversal is revealed. It is shown that the addition of Fe impurities increases the powders’ coercive force and reduces tunnel magnetoresistance. A resonance mechanism of carrier tunneling in powders of CrO₂ solid solutions with iron impurities is proposed.