Possibility of a simultaneously ferroelectric and magnetic phase transition

1)磁电测量结果表明，镍碘方铅矿Ni^3B^7O&lt；13&gt；i低温相的磁级为m‘或更低，而不是以前认为的m’m2‘。根据介电、磁学和磁电测量，我们推测该晶体在25K时存在另一种相变(将在《铁电学》上发表)，结果表明，EuMn_2O_5在40K和21K时分别发生了两次相变。40K时的转变被认为是同时具有铁电和反铁磁性质的。在类晶BiMn2O5中也发现了类似的相变。第二相变以下的EuMn235的磁级为m1‘。我们讨论了与这种对称性相容的可能的磁结构。3)介电、磁学和磁电测量表明，GdMn_2O_5在39K和26K有两个相变，分别为…更奇怪的是。39K处的转变被认为是极性/非极性类型。该晶体在第二相变以下的近似磁级为m2m1‘。GdMn2O5的磁电效应是已报道的最大的磁电效应之一。(提交固态通信)4)我们改进了先前开发的小交流磁矩检测方法。它在高温超导研究和磁电测量中具有广泛的应用前景。结果2)和3)表明组成为REMn_2O_5的稀土锰氧化物是一组非常有趣的物质，可能在某个转变时同时成为铁电和反铁磁或一般的日磁。我们现在正在继续对这一系列氧化物进行系统的研究。在上述研究活动的同时，首席研究员与K.Siratori博士和E.Kita博士一起撰写了一篇关于磁电效应的综述文章的一部分。(将发表在《波罗尼察学报》上)--

1)From the results of magnetoelectric measurements, we concluded that the magnetic class of the low temperature phase of nickel-iodine boracite Ni^3B^7O^<13>I is m' or lower, in contrast with the previous view that it was m' m 2'. We suggested the existence of another phase transition of this crystal at 25 K. (to be published in Ferroelectrics)2)From the dielectric, magnetic and magnetoelectric measurements, weconcluded that EuMn_2O_5 show two phase transitions at 40 K and 21 K, respectively. The transition at 40K was considered to be of simultaneously ferroelectric and antiferromagnetic nature. Similar transition was also found in isomorphous BiMn_2O_5. The magnetic class of EuMn_23_5 below the second transition was determined to be m 1'. We discussed possible magnetic structures compatible with this symmetry. (to be published in Phase Transitions)3)From dielectric, magnetic and magnetoelectric measurements, weconcluded that GdMn_2O_5 shows two phase transitions at 39 K and 26 K, resp … More ectively. The transitionat 39Kwas considered to be of polar/non-polar type. Approximate magnetic class of this crystal below the second transition was determined to be m 2m 1'. The magnetoelectric effect of GdMn_2O_5 is one of the largest that have been reported previously. (submitted to Solid State Communications)4)We improved the detectionmethod of small ac magnetic moment that we developed previously. It may have a wide use in high temperature superconductivity study as well as in magnetoelectric measurement. (to be published in Phase Transitions)The results 2)and 3)show that rare earth manganites with the composition REMn_2O_5 are very interesting group of substances that possibly become ferroelectric and antiferro- or generally heli-magnetic simultaneously at a certain transition. We are now continuing a systematic study of this series of oxides.Along with the above research activities, the head investigator wrote a part of a review article about magnetoelectric effect with Drs. K. Siratori and E. Kita. (to be published in Acta Physica Polonica) Less