1999 Fiscal Year Final Research Report Summary
Investigation of Magnetotransport Phenomena in Half Metallic CrO2
| Project/Area Number |
10650032
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
表面界面物性
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| Research Institution | Miyagi National College of Technology |
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Principal Investigator |
SUZUKI Katsuhiko Miyagi National College of Technology, Department of Integrated Arts and Sciences, Associate Prof., 総合科学系理数科, 助教授 (80187715)
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| Co-Investigator(Kenkyū-buntansha) |
SAWADA Anjyu Tohoku Univ., Department of Physics, Associate Prof., 大学院・理学研究科, 助教授 (90115577)
MATSUURA Makoto Miyagi National College of Technology, Department of Integrated Arts and Sciences, Prof., 総合科学系理数科, 教授 (40042262)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Half Metal / X-Ray Diffraction / Thermal Treatment / Co-Tunneling / Magnetoresistance / CVD / Quantized Energy Level / Distortion of Crystal Structure |
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| Research Abstract |
(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
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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
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