Study of Metamagnetism Based on Quadrupole Moment in High Magnetic Field

本文主要研究了在强磁场中观察到的作为变磁性的磁易轴转换。特别是对RCu_2（R=Ho，Ce）和PrZn_2进行了强磁场磁化测量。对四极矩起重要作用的UPd_3的磁化强度进行了测量，发现了基于四极矩的新的变磁转变，只有RCu_2（R=Ce，Pr，Dy，Tb）发生了磁易轴转变。在所有材料中，不同易轴态之间的能量差接近10K。这一结果表明，Cu离子和晶体结构在这种变磁转变中起着重要作用。此外，当电子处于L_2=3或2轨道态时，也存在这种跃迁。四极矩在这些材料中很重要。由于晶体电场能级的交叉，在四极矩的相互作用下，变磁转变变宽。四极矩之间的相互作用对Pr基化合物的磁性有重要影响，在UPd_3中首次观察到基于四极矩的磁性相图。还发现了由四极矩引起的新的变磁相变类型，这些结果将被分析和发表。

The magnetic easy-axis conversion observed as the metamagnetism in the high magnetic field has been mainly studied Specifically, the high-field magnetization measurement of Rcu_2(R=Ho, Ce) and PrZn_2 are carried out. The magnetization measurement of UPd_3 in which the quadrupole moment play important role, is also carried out and the new metamagnetic transition based on the quadrupole moment is found in this material.The magnetic easy-axis conversion is ony found with the RCu_2(R=Ce, Pr, Dy, Tb). The difference energy between different easy-axis states is almost 10K in the all materials. This result indicates that the Cu ion and ciystal structure is important in this metamagnetic transition. Further-more, this transition is found when the electron occupies the L_2=3 or 2 orbital state.We also measure the high-field magnetization of PrCu6_6PrNi_5. The quadrupole moment is important in these materials. The metamagnetic transition due to the crossing of the crystalline electronic field level become broad with the interaction of the quadrupole moment. The interaction between quadrupole moment is important on the Pr based compound.The magnetic phase diagram base on the quadrupole moment is firstly observed in UPd_3. New type of the metamagnetic transition due to the quadrupole moment is also found. These results will be analized and published.