Development of Giant Magnetostrictive Material by Applying Metamagnetic Transition

本课题的研究成果总结如下：1La(Fe_xSi_<1-x>)_<13>化合物La(Fe_xSi_<1-x>)_<13>化合物（0.86【小于或等于】x【小于或等于】0.90）在居里温度Tc ~ 200K以上表现出流动电子的超磁致伸缩。约1.5%的体积变化是由相变时约1μ_B的磁化强度变化引起的。为了将体积变化应用于磁致伸缩材料，通过吸氢将居里温度控制到室温。对于La (Fe_<0.88>Si_<0.12>)_<13>H_<1.0>的化合物，室温下T_c值升高至278 K，并观察到与传统Tafenol相当的大各向同性体积磁致伸缩。由于La (Fe_xSi_<1-x>)_<13>H_y化合物的磁致伸缩具有与传统材料相当的大幅度和各向同性的特点，这些化合物可以成为新型的磁致伸缩材料，从而消除了器件构造中的结构控制等过程多磁相变La (Fe_xAl_<1-x>)_<13>化合物的磁体积效应和磁致伸缩研究La (Fe_xAl_<1-x>)_<13>化合物在0.60 <小于等于x <等于0.86时为铁磁性，而在0.87 <小于等于x <等于0.92时为反铁磁性。此外，磁场诱导的一阶跃迁出现在反铁磁相中。此外，在0.86<x<0.87的转变温度T_0处观察到热诱导的一阶转变。在流动电子磁体中，磁矩的幅值在相变过程中随体积变化而变化。通过T_0附近的热膨胀测量，观察到各向同性体积变化约0.5%。进一步证实了x = 0.88时磁场诱导的反铁磁-铁磁跃迁会引起各向同性体积磁致伸缩。结果表明，由于化合物中各种磁相变引起的磁矩幅值的显著变化，出现了大的各向同性体积磁致伸缩。少

Research results of the present project is summarized as follows.1 Study on Isotropic Giant Magnetostriction of Itinerant-Electron Metamagnetic La (Fe_xSi_<1-x>)_<13> CompoundsLa(Fe_xSi_<1-x>)_<13> Compounds (0.86【less than or equal】x【less than or equal】0.90) exhibit the itinerant-electron metamagnetic transition just above the Curie temperature Tc〜200K. Volume change of about 1.5% is caused by a change in magnetization of about 1μ_B at the transition. To apply the volume change to magnetostrictive materials, the Curie temperature was controlled up to room temperature by hydrogen absorption. For La (Fe_<0.88>Si_<0.12>)_<13>H_<1.0> compound, the value of T_c was elevated up to 278 K, and large isotropic volume magnetostriction comparable in that of conventional Tafenol has been observed around room temperature. Since, the magnetostriction of La (Fe_xSi_<1-x>)_<13>H_y compounds show both the large magnitude comparable to those to the conventional materials and the isotropic feature, the … More compounds can be new magnetstrictive materials which remove the process such as the structural control in constructon of devices.2 Study on Magnetovolume Effect and Magnetostriction in La (Fe_xAl_<1-x>)_<13> Compounds showing Multiple Magnetic Phase TransitionLa (Fe_xAl_<1-x>)_<13> Compounds are ferromagnetic in 0.60【less than or equal】x【less than or equal】0.86, while become antiferromagnetic in 0.87【less than or equal】x【less than or equal】0.92. Furthermore, the magnetic field induced first-order transition to the ferromagnetic state appears in the antiferromagnetic phase. In addition, the thermal induced first-order transition has been observed at the transition temperature T_0 in 0.86<x<0.87. In the itinerant-electron magnets, amplitude of magnetic moment varies in these phase transition followed by volume change. By thermal expansion measurement around T_0, the isotropic volume change of about 0.5 % has been observed. Furthermore, it has been confirmed that the isotropic volume magnetostriction is induced by the magnetic field induced antiferromagnetic-ferromagnetic transition for x = 0.88. Consequently, it has been demonstrated that large isotropic volume magnetostriction is appeared by significant change in amplitude of magnetic moment due to the various magnetic phase transitions in the present compounds. Less