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

在这项工作中，我通过高x射线衍射测量研究了新型磁性制冷剂。我已经澄清了一些主题如下：1。在大磁热材料MnFeP_0.5As_0.5上观察到场致磁性和结构转变。材料具有六角形结构，在磁场作用下参数a和c的变形量分别为0.5%和1.0%。大磁热材料Gd_5(GeFe)Si_2在强磁场作用下由单斜向正交结构转变。在大磁热材料Ni_<50>Mn_<36>Sn_<14>中观察到场致反马氏体相变，由正交结构向立方结构转变。铁磁性形状记忆合金Ni_<50>Mn_<36>Sn_<14>表现出较大的磁阻效应，并伴有场致反向马氏体相变。研究了磁性形状记忆合金Ni_<50>Mn_<36>Sn_<14>在强磁场下的磁性和热电性能。在高磁场作用下，在630 K高温下观察到MnBi的一阶变磁转变。MnBi在一阶磁转变温度下表现出较大的磁热效应。在高磁场作用下，MnBi的一阶磁转变温度以2 KT^<-1>.8的速率升高。DyB_2C_2在10 K以下发生了磁场和压力诱导的磁跃迁。

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.