Wang Hui, Zhang Yang, Tachiyama Koki, Xia Zhaoyang, Fang Jinghong, Li Qin, Cheng Guofeng, Shi Yun, Yu Jianding, Katayama Tsukasa, Yasui Shintaro, Itoh Mitsuru
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050, China.
Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
Inorg Chem. 2021 Jan 4;60(1):225-230. doi: 10.1021/acs.inorgchem.0c02855. Epub 2020 Dec 15.
GaFeO-type iron oxides are promising multiferroics due to the coexistence of large spontaneous magnetization and polarization near room temperature. However, the high leakage current and difficulties associated with synthesizing single crystals make it difficult to achieve two important features in the system: a large ferroelectric polarization switching and magnetoelectric coupling at a high-temperature region. Herein, we report successful achievement of these features by preparing high-quality Sc-doped GaFeO single crystals (ScGaFeO with = 0-0.3) using the floating zone method. The ≥ 0.05 crystals exhibit a leakage current 10 times lower than the = 0 crystals, highlighting the importance of Sc doping. Because of the reduced leakage current, the Sc-doped crystals exhibit large ferroelectric polarization switching along the -axis with a remanent polarization of 22-25 μC/cm, which is close to the theoretically predicted polarization value of 25-28 μC/cm. In addition, the Sc-doped crystals exhibit ferrimagnetism with magnetic anisotropy along the -axis. Furthermore, a magnetic-field-induced modulation of polarization is observed in the = 0.15 crystal even at a relatively high temperature, i.e., 100 K.
由于在室温附近存在大的自发磁化和极化，GaFeO型铁氧化物是很有前景的多铁性材料。然而，高漏电流以及与合成单晶相关的困难使得在该体系中难以实现两个重要特性：大的铁电极化翻转以及高温区域的磁电耦合。在此，我们报道通过使用浮区法制备高质量的Sc掺杂GaFeO单晶（ScGaFeO，x = 0 - 0.3）成功实现了这些特性。x≥0.05的晶体漏电流比x = 0的晶体低10倍，突出了Sc掺杂的重要性。由于漏电流降低，Sc掺杂的晶体沿c轴表现出大的铁电极化翻转，剩余极化强度为22 - 25 μC/cm²，这接近理论预测的25 - 28 μC/cm²的极化值。此外，Sc掺杂的晶体表现出沿c轴具有磁各向异性的亚铁磁性。而且，即使在相对较高的温度（即100 K）下，在x = 0.15的晶体中也观察到了磁场诱导的极化调制。
