水热法制备的冷压CrO $_2$粉末的输运和磁输运性质
Transport and magnetotransport properties of cold-pressed CrO$_2$ powder, prepared by hydrothermal synthesis
摘要：
以三氧化铬为原料，采用水热法制备了亚微米级氧化铬$_2$粉体。所得颗粒为圆形，平均直径约为120 nm。用结构、X-射线和磁性测量对粉末（表面有β-CrOOH薄层稳定）进行了表征。对居里温度约为385 K的粉末进行冷压，并在4--450 K温度范围内，在磁场~ 1.6 T范围内测量了其输运和磁输运性质。所研究的样品具有非金属的电阻温度行为，在低温区具有较大的负磁阻效应。在T=5 K时，MR幅度在H=0.3 T时为-17%，在H=1.4 T时为-20%。随着温度的升高，其幅值迅速减小，当T>200 K时，其幅值小于0.3%.结果表明，这种MR行为是固有的系统的磁性晶粒与自旋相关的晶粒间隧穿。在低温范围内（低于40 K）的MR行为的一些特点可以与此颗粒系统的隧道电导率的可利用性的条件下，只有几个导电电流路径通过样品的特性。
英文摘要：
Submicron powder of CrO$_2$ was prepared by hydrothermal synthesis method from chromium trioxide. Particles obtained were of rounded form with mean diameter about 120 nm. The powder (stabilized with thin surface layer of β-CrOOH) has been characterized by structural, X-ray and magnetic measurements. The powder (with Curie temperature about 385 K) was cold-pressed and its transport and magnetotransport properties have been measured in the temperature range 4--450 K in magnetic field up to 1.6 T. The samples studied is characterized by non-metallic temperature behavior of resistance and large negative magnetoresistance (MR) in low temperature range. At T=5 K the MR magnitude has been -17% at H=0.3 T and -20% at H=1.4 T. Its magnitude decreased fast with increase in temperature reducing to 0.3% and less for T>200 K. It is shown that this MR behavior is inherent for a system of magnetic grains with spin-dependent intergrain tunnelling. Some peculiarities of MR behavior in low-temperature range (below 40 K) can be associated with percolating character of tunnelling conductivity of this granular system under conditions of availability of only few conducting current paths through the sample.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
