Magnetic Properties and Structure of Icosahedral Cluster Alloys

研究了3d过渡金属晶体和由二十面体团簇组成的非晶态合金的自旋涨落、磁体效应、变磁相变和低温比热。主要结果如下：1)La(Fe_xAl_1&lt；-x&gt；)_&lt；13&gt；的磁相图和自旋涨落与Moriya-Usami提出的自旋涨落理论预测的相图非常相似。2)La(Fe_xSi1_&lt；-x&gt；)_&lt；La(Fe_xSi_&lt；1-x&gt；)_&lt；13&gt；在居里温度以上发生磁变后，观察到了巨磁体积效应。从实用的角度研究了居里温度的控制，证实了Co的加入是有效的。3)比较了La(Co&lt；1-x&gt；Mn_x)_13&gt；晶态和非晶态的磁特性，非晶态和晶态的磁矩随浓度变化不同。4)La(Co_&lt；1-x&gt；Tm_x)_&lt；13&gt；非晶态合金的结构研究了La(Co_&lt；1-x&gt；Crx)_13&gt；13&gt；和La(Co_&lt；1-x&gt；Mn_x)_&lt；13&gt；指出后一种合金中的二十面体团簇发生了形变。这种差异是由锰和铬之间的原子尺寸差异来解释的。

Spin fluctuations, magnetovolume effects, metamagnetic transition, low temperature specific heat of 3d transition metal crystals and amorphous alloys composed of icosahedral clusters have been investigated. The main results are summarized as follows :1) Magnetic phase diagram and spin fluctuations of La(Fe_xAI1_<-x>)_<13>Magnetic phase diagram near the phase boundary between the antiferromagnetism and the ferromagnetism is very similar to the phase diagram predicted by the spin fluctuation theory proposed by Moriya-Usami.2) Giant volume magnetostriction and the control of the Curie temperature of La(Fe_xSi1_<-x>)_<13>After the metamagnetic transition just above the Curie temperature, a giant magnetovolume effect has been observed in La(Fe_xSi_<1-x>)_<13>. From the practical point of view, the control of the Curie temperature has been investigated and it has been confirmed that the addition of Co is effective.3) Comparison between magnetic properties of La(Co_<1-x>Mn_x)_<13> in crystalline and amorphous states.The concentration dependence of the magnetic moment in the amorphous state is different from that in the crystalline state. The concentration range where the icosahedral clusters are formed for the amorphous alloys is wider than that for the crystalline alloys.4) Structures of La(Co_<1-x>TM_x)_<13> amorphous alloys.Structural differences between La(Co_<1-x>Cr_x)_<13> and La(Co_<1-x>Mn_x)_<13> amorphous alloys have been investigated. it has been pointed out that the icosahedral clusters in the latter alloys are deformed. Such a difference is explained by the atomic size difference between Mn and Cr.