Crystal Phase Transition Induced by Magnetic Field.

本文用X射线衍射技术研究了重稀土金属Dy，Ho和Er的磁场诱导相变，得到以下结果：（1）在螺旋相中观察到Dy的c晶格参数随磁场的变化，发现在低温下为一级相变，而在Neel温度附近为二级相变。在磁场作用下的螺旋相中，观察到晶格调制，其调制幅度随磁场的增加而增加。(2)研究了Ho的c晶格参数随螺旋-螺旋扇-扇-铁磁跃迁的变化。在螺旋相和螺旋扇相也发现了晶格调制，并详细研究了螺旋扇结构出现的温度和磁场范围。(3)确定了Er的温度-磁场磁相图。晶格调制表现出相当复杂的行为，这是由复杂的磁结构的影响。根据晶格调制的实验结果，确定了中子衍射中不确定的高场区的磁结构。

Magnetic field induced phase transitions of heavy rare earth metals Dy, Ho and Er have been investigated by means of x-ray diffraction technique and following results have been obtained :(1) The magnetic field dependence of the c-lattice parameter in Dy has been observed in the helix phase and the phase transition has been found to be the first order at low temperatures while it exhibits the second order transition near the Neel temperature. In the helix phase under magnetic field, the lattice modulation has been observed, which increases the modulation amplitude with increasing magnetic field.(2) The change of the c-lattice parameter of Ho accomanying to the helix-helifan-fan-ferro transtition has been studied. The lattice modulation is also found in helix and helifan phase and the range of the temperature and magnetic field for appearance of the helifan structure has been studied in detail.(3) The magnetic phase diagram of temperature and magnetic field has been determined for Er. The lattice modulation exhibits rather complicated behavior which is affected by the complicated magnetic structures. The magnetic structure at high field region which was unsure in neutron diffraction has been determined from the experimental results of the lattice modulation.