Experimental studies of novel magnetic refrigerants by high field X-ray diffraction measurements

点击翻译按钮获取中文摘要

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.