The Cr O2 micro rod powder was synthesized by decomposing the Cr O3 flakes at a specific temperature to yield precursor and annealing such a precursor in a sealed glass tube. The magneto-transport properties have been...The Cr O2 micro rod powder was synthesized by decomposing the Cr O3 flakes at a specific temperature to yield precursor and annealing such a precursor in a sealed glass tube. The magneto-transport properties have been measured by a direct current four-probe method using a Cu/Cr O2rods/colloidal silver liquid electrode sandwich device. The largest magnetoresistance(MR) around *72 % was observed at 77 K with applied current of 0.05 l A. The non-linear I–V curve indicates a tunneling type transport properties and the tunneling barrier height is around 2.2 ± 0.04 e V at 77 K, which is obtained with fitting the non-linear I–V curves using Simmons' equation. A mixing of Cr oxides on the surface of Cr O2 rod observed by X-ray photoemission spectroscopy provides a tunneling barrier rather than a single phase of Cr2O3 insulating barrier. The MR shows strong bias voltage dependence and is ascribed to the two-step tunneling process.展开更多
CrO_(2)-TiO_(2) composites are synthesized by using a high temperature and high pressure method using CrO_(3) and H_(2)TiO_(3) as precursors.The composites consist of large rod-like CrO_(2) crystals separated by small...CrO_(2)-TiO_(2) composites are synthesized by using a high temperature and high pressure method using CrO_(3) and H_(2)TiO_(3) as precursors.The composites consist of large rod-like CrO_(2) crystals separated by small TiO_(2) grains.The CrO_(2) in the composites is very pure and its saturation magnetization is very close to the theoretical value(i.e.,2μ_(B) per formula unit).The composites exhibit a large negative magnetoresistance(MR)at 5 K.The MR in CrO_(2)-TiO_(2) composites is mainly attributed to spin-polarized tunneling between CrO_(2) crystals.The conductivity of the composites is best described by a fluctuation-induced tunneling model below 230 K.展开更多
基金supported by the NNSF of China (Nos. 51171076, 51101079)the Natural Science Foundation of Gansu Province (No. 145RJZA154)+1 种基金the Fundamental Research Funds for the Central Universities (No. Lzujbky-2012-27, Lzujbky-2010172)the CERS of China (No. CERS-1-89)
文摘The Cr O2 micro rod powder was synthesized by decomposing the Cr O3 flakes at a specific temperature to yield precursor and annealing such a precursor in a sealed glass tube. The magneto-transport properties have been measured by a direct current four-probe method using a Cu/Cr O2rods/colloidal silver liquid electrode sandwich device. The largest magnetoresistance(MR) around *72 % was observed at 77 K with applied current of 0.05 l A. The non-linear I–V curve indicates a tunneling type transport properties and the tunneling barrier height is around 2.2 ± 0.04 e V at 77 K, which is obtained with fitting the non-linear I–V curves using Simmons' equation. A mixing of Cr oxides on the surface of Cr O2 rod observed by X-ray photoemission spectroscopy provides a tunneling barrier rather than a single phase of Cr2O3 insulating barrier. The MR shows strong bias voltage dependence and is ascribed to the two-step tunneling process.
基金Supported by the National Natural Science Foundation of China under Grant No 50972048the Program for New Century Excellent Talents in University.
文摘CrO_(2)-TiO_(2) composites are synthesized by using a high temperature and high pressure method using CrO_(3) and H_(2)TiO_(3) as precursors.The composites consist of large rod-like CrO_(2) crystals separated by small TiO_(2) grains.The CrO_(2) in the composites is very pure and its saturation magnetization is very close to the theoretical value(i.e.,2μ_(B) per formula unit).The composites exhibit a large negative magnetoresistance(MR)at 5 K.The MR in CrO_(2)-TiO_(2) composites is mainly attributed to spin-polarized tunneling between CrO_(2) crystals.The conductivity of the composites is best described by a fluctuation-induced tunneling model below 230 K.
