Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China.
Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
Sci Rep. 2016 Oct 7;6:34767. doi: 10.1038/srep34767.
The magnetically induced electric polarization behaviors in multiferroic TmMnO in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed. The temperature-dependent electric polarization flop as a major character is identified for different measuring paths. The magneto-current measurements indicate that the electric polarization in the low temperature magnetic phase region has different origin from that in the high temperature magnetic phase. It is suggested that the electric polarization does have multiple components which align along different orientations, including the Mn-Mn-Mn exchange striction induced polarization P, the Tm-Mn-Tm exchange striction induced polarization P, and the low temperature polarization P probably associated with the Tm commensurate phase. The observed electric polarization flop can be reasonably explained by the ferrielectric model proposed earlier for DyMnO, where P and P are the two antiparallel components both along the b-axis and P may align along the a-axis. Finally, several issues on the unusual temperature dependence of ferroelectric polarizations are discussed.
多铁性 TmMnO 中磁致电极化行为随温度和磁场的变化关系，采用包括高精度热释电流技术在内的一系列特性分析方法进行了仔细研究。这里使用多晶而不是单晶样品，以避免单晶中强烈的自极化效应，并进行了各种排除热激发电流贡献的平行实验。对于不同的测量路径，确定了温度相关的电极化反转作为主要特征。磁电流测量表明，低温磁相区的电极化与高温磁相区的电极化具有不同的起源。这表明电极化具有多个沿不同方向排列的分量，包括 Mn-Mn-Mn 交换伸缩诱导的极化 P、Tm-Mn-Tm 交换伸缩诱导的极化 P 和可能与 Tm 共格相相关的低温极化 P。通过早期提出的用于 DyMnO 的铁电模型，可以合理地解释观察到的电极化反转，其中 P 和 P 是沿 b 轴的两个反平行分量，而 P 可能沿 a 轴排列。最后，讨论了铁电极化的异常温度依赖性的几个问题。
