Electric and Magnetic Low-Temperature Phase Transitions of YbMn_2O_5

抄録

We made measurements of dielectric constant, pyroelectric current, magnetic susceptibility and magnetoelectric effect of single crystals of YbMn₂O₅. From the results, we concluded that there were two phase transitions besides antiferromagnetic transition at approximately 40, K.The first transition at 32, K is characterized by a peak of dielectric constant, a kink of magnetoelectric polarization and an appearance of pyroelectricity below this temperature. It was considered to be electric in nature. The second one is at 6, K. It is also accompanied by another peak of dielectric constant, a steep rise of pyroelectricity and anomalies of both magnetic and magnetoelectric susceptibilities. We suppose that the ordering of Yb³⁺ magnetic moments begins to develop at this temperature, involving a change in the crystal structure and then in spontaneous polarization. The low temperature phase has a magnetic field-induced transition which occurs at about 19, kOe at 4.2, K.