Vortex ferroelectric domains, large-loop weak ferromagnetic domains, and their decoupling in hexagonal (Lu, Sc)FeO3

Kai Du,Rongwei Hu,Sang-Wook Cheong,Bin Gao,Fei-Ting Huang,Yazhong Wang,Xianghan Xu,Jaewook Kim

doi:10.1038/s41535-018-0106-3

Kai Du, Rongwei Hu + Show 6 more

Open Access

https://doi.org/10.1038/s41535-018-0106-3

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Abstract

The direct domain coupling of spontaneous ferroelectric polarization and net magnetic moment can result in giant magnetoelectric (ME) coupling, which is essential to achieve mutual control and practical applications of multiferroics. Recently, the possible bulk domain coupling, the mutual control of ferroelectricity (FE) and weak ferromagnetism (WFM) have been theoretically predicted in hexagonal LuFeO3. Here, we report the first successful growth of highly-cleavable Sc-stabilized hexagonal Lu0.6Sc0.4FeO3 (h-LSFO) single crystals, as well as the first visualization of their intrinsic cloverleaf pattern of vortex FE domains and large-loop WFM domains. The vortex FE domains are on the order of 0.1–1 μm in size. On the other hand, the loop WFM domains are ~100 μm in size, and there exists no interlocking of FE and WFM domain walls. These strongly manifest the decoupling between FE and WFM in h-LSFO. The domain decoupling can be explained as the consequence of the structure-mediated coupling between polarization and dominant in-plane antiferromagnetic spins according to the theoretical prediction, which reveals intriguing interplays between FE, WFM, and antiferromagnetic orders in h-LSFO. Our results also indicate that the magnetic topological charge tends to be identical to the structural topological charge. This could provide new insights into the induction of direct coupling between magnetism and ferroelectricity mediated by structural distortions, which will be useful for the future applications of multiferroics.

Highlights

Multiferroic materials, in which two or multiple ferroic orders coexist, have drawn a great deal of attentions due to their fundamental importance and potentials for the generation devices.[1–3] in most multiferroics, the magnetoelectric (ME) coupling strength is quite weak, especially in linear-ME materials,[4] which limits their practical applications
A theoretical study suggests that the single-phase hexagonal LuFeO3 (h-LuFeO3) system may have the potential to realize this ideal effect with the direct domain coupling between its ferroelectricity (FE) and weak ferromagnetism (WFM).[10]
The recent ME coupling study on h-LuFeO3/LuFe2O4 superlattices[11] demonstrates the capability of electrical field control of magnetism near the room temperature, which indicates h-LuFeO3 and its related compounds are promising for future applications

Summary

INTRODUCTION

Multiferroic materials, in which two or multiple ferroic orders coexist, have drawn a great deal of attentions due to their fundamental importance and potentials for the generation devices.[1–3] in most multiferroics, the magnetoelectric (ME) coupling strength is quite weak, especially in linear-ME materials,[4] which limits their practical applications. For the possible giant ME coupling, h-LuFeO3 systems in the P63cm polar structure (Fig. 1a) has attracted a significant research attentions, since this metastable hexagonal phase of its orthorhombic bulk form was reported to be stabilized in thin film form by epitaxial strain[12,13] or in bulk by Sc or Mn doping.[14–16]. Samples in both forms are believed to show similar physical properties despite different approaches used for the synthesis (see Supplementary Information, note 1 for details). H-LuFeO3 is a unique candidate where a direct mutual control of P and M domains can be explored

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