Features of Low Temperature Tunnel Magnetoresistance in Pressed Powder of Chromium Dioxide

Resistive and magnetoresistive properties of two samples of compacted powders of ferromagnetic half-metal CrO_{2} with shape anisotropy of nanoparticles were studied. The powders were prepared by the method of hydrothermal synthesis and consisted of needle-like particles with average diameters 24-34 nm and mean length of 300 nm. One of the samples has been made of compacted powder of pure CrO_{2}, while another sample has been prepared from a substitution solid solution Cr_{1-x}Fe_{x}O_{2}. The aim of this work was to study the effect of Fe impurity on the value of tunnel resistance and tunnel magnetoresistance for compacted CrO_{2} powders. It was found that the addition of Fe impurity leads to an increase in the coercive force of the powder and reduce the tunnel magnetoresistance. We assume resonant tunneling mechanism on the Fe impurities. We found a strong dependence of the magnetoresistance on the spin relaxation rate in the process of magnetization reversal. The possible reasons for such dependence are discussed.