Influence Of High-Pressure And High-Temperature On Tunneling Magnetoresistance Effect Of CrO₂ Nanometer Structure

In recent years, spin-electronics is one of the focuses of the international condensed matter physics and material sciences, so it attracts much attention. As the simplest ferromagnetic half-metal oxide, Chromium dioxide is the traditional magnetic recording material and its Curie temperature Tc is high to 396K. Consequently, CrO₂ is considered to be an ideal,potential material in spintronic devices.This paper adopts cold-pressed and hot-pressed methods to modulate the interfaces condition of the CrO₂ samples. Using different testing and analyzing means, we studied the magnetic and electric properties of CrO₂ bulk samples, especially the tunneling magnetoresistance effect of the samples. We also analyzed the varieties of the configuration and condition in the interfaces with compacting temperature and pressure.The particles of cold-pressed samples is nanometer particles. The cold-pressed samples have big coercivity and remanence at low temperature. It happens the phenomenon of pressure-induced crystallite breaking in the samples at high pressure. With the increase of compacting pressure, the particle size diminishes and the aspect ratio reduces, thus the coercivity and remanence decrease. At low temperature (T<50K), the spin-dependent intergranular tunneling across the grain boundaries induced by the Coulomb block is the dominant transport mechanism. At high temperature, the inelastic hopping of spin-independent electrons through the localized states induced by vices and impurities in the grain-boundary barrier occupies the dominant status. With the increase of temperature, the contribute of the spin-independent high-order inelastic hopping course induced by localized states increases, which induces the magnetoresistance of cold-pressed samples...