Search for a new phase of multiferroic ferroelectric RFe2O4 aimed at practical applications

为了寻找室温下的多铁性，我们进行了电子铁电RFe2O4(R：稀土)的研究工作。通过几种尝试，如R位和Fe位的取代，磁性转变温度并没有发生明显的变化。然而，相关体系R2Fe3O7在270K出现了磁相变，比RFe2O4高出20K。据报道，R2Fe3O7在室温下是铁电的，在270K以下是多铁的，这一结果提供了将转变温度提高到室温的可能性。此外，我们还发现了RFe2O4的几个新现象，如电流引起的交换偏置和增强各向异性，这些现象可能被用来制作新的多铁性器件。

In search of multiferroiciity at room temperature, we have conducted the research work on electronic ferroelectric RFe2O4 (R: rare earths). The magnetic transition temperature was not drastically changed by a few kinds of attempts, such as R- and Fe-sites substitutions. However, it was found that the related system R2Fe3O7 shows a magnetic transition at 270 K, which is 20 K higher than that of RFe2O4. As R2Fe3O7 was reported to be ferroelectric at room temperature, this system is multiferroic below 270 K. This result offers a possible increase in transition temperature up to room temperature. In addition, we have revealed several new phenomena of RFe2O4, such as exchange bias and enhancement anisotropy induced by electrical current, which may be used to fabricate new multiferroic devices.