Lee Bo Wha, Yoo Pil Sun, Nam Vu Binh, Toreh Kirstie Raquel Natalia, Jung Chang Uk
Department of Physics, Hankuk University of Foreign Studies, 81 Oedae-ro, Mohyeon-myeon, Cheoin-gu, Yongin, 449-791 Korea.
Nanoscale Res Lett. 2015 Feb 6;10:47. doi: 10.1186/s11671-015-0759-9. eCollection 2015.
It has been suggested that BiMnO3 is a material exhibiting both ferromagnetism and ferroelectricity. Stoichiometry is rather easily achieved in a polycrystalline sample, and ferromagnetic properties have been well documented for bulk samples. Stoichiometry in thin films has been difficult to obtain, and many physical properties have exhibit wide distributions mainly due to the stoichiometry problem. Thin film studies on BiMnO3 have not shown clear evidence of ferroelectricity, while other physical properties measured for the BiMnO3 films showed wide spectra, which has been attributed to cation and/or oxygen vacancies. We fabricated BiMnO3 thin films with good stoichiometry and with ferromagnetic properties comparable to those reported for stoichiometric BiMnO3: Tc ~ 105 K and M sat ~ 3.6 μB/Mn. The charge-electric field (Q-E) curve measured at 5 K was fairly linear and free from hysteresis and showed no ferroelectric order. This finding is consistent with the centrosymmetric crystal structure recently suggested by theoretical calculations and structural studies on ceramic samples of stoichiometric BiMnO3.
有人提出，BiMnO₃是一种兼具铁磁性和铁电性的材料。在多晶样品中相当容易实现化学计量比，并且块状样品的铁磁性能已有充分记录。在薄膜中难以获得化学计量比，并且许多物理性质呈现出广泛的分布，这主要归因于化学计量比问题。对BiMnO₃薄膜的研究尚未显示出铁电性的明确证据，而对BiMnO₃薄膜测量的其他物理性质显示出宽广的谱线，这归因于阳离子和/或氧空位。我们制备了具有良好化学计量比且具有与化学计量比BiMnO₃报道的相当的铁磁性能的BiMnO₃薄膜：居里温度Tc约为105 K，饱和磁化强度Msat约为3.6 μB/Mn。在5 K下测量的电荷-电场（Q-E）曲线相当线性且无滞后现象，并且未显示出铁电有序。这一发现与最近通过对化学计量比BiMnO₃陶瓷样品的理论计算和结构研究提出的中心对称晶体结构一致。
