Magnetotransport properties of CrO2 powder composites (Review article)

The most significant experimental results and theoretical concepts related to chromium dioxide-based composites, according to their influence on the evolution of modern understanding of electron transport phenomena in disordered magnetic systems, are presented. It is shown that the variety of physical processes taking place in powder materials does not allow the development of a holistic theoretical approach to describing the properties of the obtained compacted materials. The properties of composite materials depend on the anisotropy of the shape and magnetic properties of particles of which they are composed. The influence of percolation effects leads to a change in the current-carrying channels morphology with the temperature variation in an external magnetic field. This affects both the shape of the magnetoresistance hysteresis loops and the magnetic field magnitudes corresponding to the magnetoresistance maxima. A wide range of magnetotransport phenomena observed in half-metal composite materials contributes to the development of modern concepts of the conductivity features near the metal-insulator threshold and the influence of the metal-insulator interfaces on tunneling conductivity.