| Project/Area Number |
17560610
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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 |
Structural/Functional materials
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| Research Institution | Tohoku University |
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Principal Investigator |
KOYAMA Keiichi Tohoku University, Institute for Materials Research・Tohoku University, Associate Professor (70302205)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,310,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥210,000)
Fiscal Year 2007: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | high magnetic field / powder X-ray diffraction / crystal structure / magnetic refrigerant / lst-order phase transition / magnetocaloric effect / structural transformation / 高磁気熱量材料 / 包晶反応 / スピン再配列 / X線回折装置 / 磁気体積効果 / 磁気冷凍 / 低温 / 高磁気熱材料 / 高磁歪材料 / 磁場誘起形状記憶強磁性体 |
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| Research Abstract |
In this work, I have studied novel magnetic refrigerants by high X-ray diffraction measurements. I have clarified some topics as follows:
1. I observed a field-induced magnetic and structural transition on large magnetocaloric material MnFeP_0.5As_0.5. The material has a hexagonal structure and shows that the parameters a and c deform by 0.5% and 1.0%, respectively, by magnetic field.
2. Large magnetocaloric material Gd_5(GeFe)Si_2 shows a structural transformation from a monoclinic structure to an orthorhombic structure by high magnetic field.
3. I observed a field-induced reverse martensitic transformation from an orthorhombic structure to a cubic structure in large magnetocaloric material Ni_<50>Mn_<36>Sn_<14>.
4. The ferromagnetic shape memory alloy Ni_<50>Mn_<36>Sn_<14> shows a large magnetoresistance effect accompanied by the field-induced reverse martensitic transformation.
5. I revealed the magnetic and thermoelectric properties of magnetic shape memory alloy Ni_<50>Mn_<36>Sn_<14> in high magnetic fields.
6. I observed a metamagnetic (1st-order) transition of MnBi at high temperature of 630 K by high magnetic fields.
7. MnBi shows a large magnetocaloric effect at the 1st-order magnetic transition temperature. By applying high magnetic field, the 1st-order magnetic transition temperature of MnBi increases at the rate of 2 KT^<-1>.
8. Magnetic field and pressure induced magnetic transitions were observed in DyB_2C_2 below 10 K.
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