Study of Metamagnetism Based on Quadrupole Moment in High Magnetic Field

重点研究了在强磁场中观察到的超磁效应的磁易轴转换现象，对RCu2(R=Ho，Ce)和PrZn2的高场磁化强度进行了测量。测量了UPd_3的磁化强度，发现了新的基于四极矩的变磁相变。RCu2(R=Ce，Pr，Dy，Tb)的磁易轴转换是唯一的。在所有材料中，不同易轴态之间的能量差几乎为10K。这一结果表明，铜离子和晶体结构在这一变磁转变中起着重要的作用。此外，我们还测量了PrCu6_6PrNi_5的高场磁化强度。四极矩在这些材料中是重要的。在四极矩的作用下，晶态电场能级交叉引起的超磁相变变宽。在Pr基化合物中，四极矩之间的相互作用是非常重要的。在UPd_3中首次观察到了基于四极矩的磁相图，并发现了由四极矩引起的新型亚磁相变。这些结果将被分析并公布。

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.