Investigation of Magnetotransport Phenomena in Half Metallic CrO2

(1)结果发现，CrO 2膜选择性地沉积到图案化的TiO 2膜的热氧化的Ti膜在玻璃基板上的CVD方法。隧道结是用这种技术制成的。虽然隧道电阻的值是足够的，TMR性能并没有显示出良好的数据。通过使CrO 2膜与绝缘体之间的界面光滑，可以改善性能。(2)在10 T以下的温度范围内测量了ZrO 2衬底上只有（100）织构的CrO 2薄膜的电阻率和磁电阻。电阻率随温度变化的形状可以用半金属的描述和T_（？）2依赖性和电子比热表明CrO_2属于重费米子。通过对磁电阻数据的分析得到的参数值包含了平均自由程的信息， ...更多信息 当温度低于5 K时，自旋反转散射的强度突然增加，这表明由于半金属的存在，磁振子激发导致自旋反转散射过程的缺乏。(3)在（110）取向的TiO 2/Si（111）衬底上生长的（100）CrO 2薄膜的负磁电阻值大于在ZrO 2衬底上生长的（100）CrO 2薄膜的负磁电阻值。(4)在473 K退火后，CrO 2薄膜的负磁电阻（MR）在20 K以上增大，在20 K以下减小; 473 K退火后，CrO 2薄膜a轴晶格间距增大，能带计算和WKB近似表明，负磁电阻的大小随着退火温度的升高而增大. (5)发现了磁电阻的磁场依赖性的阶梯模式，阶梯的高度在恒定电流下是恒定的，且与电流成反比，即阶梯在每个恒定电压区间都发生变化。这些现象可以通过薄膜中多隧道结的共隧穿来解释。少

(1) It was found that the CrO2 film is selectively deposited onto the patterned TiO2 film by the thermal oxidation of the Ti film on the glass substrates in terms of CVD method. The tunnel junction was made using the technique. Although the value of tunnel resistance was adequate, the TMR properties did not show the good data. The properties may be improved by making the interface between the CrO2 film and insulator smooth.(2) The resistivity and magnetoresistance of the CrO2 film with only (100) texture on the ZrO2 substrate were measured in the wide temperature range up to 10T.The shape of the temperature dependence of resistivity can be interpreted by the description of the half metal and the relation of the values of the coefficient of T^2 dependence and electronic specific heat suggested the CrO2 belongs to the group of the heavy fermion. The value of the parameters obtained by the analysis of the data of the magnetoresistance contain the information on the mean free path and they … More suddenly increased below about 5K, which shows the lack of spin flip scattering process by magnon excitation because of the half metal.(3) The magnitude of the negative magnetoresistance of (100) CrO2 film on TiO2/Si (111) with (110) orientation was larger than that of (100) film on ZrO2 substrate.(4) By the annealing at 473K, the magnitude of the negative magnetoresistance (MR) of the CrO2 film on TiO2/glass became large above about 20K, while the magnitude small below about 20K.The lattice spacing of a-axis was extented by the annealing at 473K.The band calculation and WKB approximation suggest that the magnitude of MR becomes by this extension.(5) The staircase pattern in magnetic field dependence in magnetoresistance was found. The step height of the staircase was constant under a constant current and reciprocal to the current, which means that the steps change at each the constant voltage interval. These phenomena can be interpreted by co-tunneling of the multi-tunnel junctions contained in the films. Less