Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic

Abstract

Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3-the geometric ferroelectric with the greatest known planar rumpling-we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially-from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

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

“…10 Thus, it is of great importance to study experimentally the possibility of a direct domain coupling effect in h-LuFeO 3 , which is energy efficient and highly desirable for future applications. Meanwhile, the recent ME coupling study on h-LuFeO 3 /LuFe 2 O 4 superlattices 11 demonstrates the capability of electrical field control of magnetism near the room temperature, which indicates h-LuFeO 3 and its related compounds are promising for future applications. However, with little knowledge of the intrinsic ME coupling of hLuFeO 3 itself, a full understanding of the ME coupling in superlattices and other related materials is unrealistic.…”

Electronic structure and direct observation of ferrimagnetism in multiferroic hexagonal YbFeO3

“…[18][19][20] The spontaneous magnetization is along the c axis. Recent work demonstrated that a super-lattice structure of hexagonal LuFe-O materials are promising for realizing room temperature multiferroic materials with co-existing ferroelectricity and ferromagnetism, 21 a property that has potential application in energy-efficient information processing and storage 22 .…”

Effects of biaxial strain on the improper multiferroicity inh−LuFeO3films studied using the restrained thermal expansion method

“…The elucidation of the strain effect in h-LuFeO 3 is an important advancement of our understanding on the coupling between the lattice and the improper multiferroicity. It is essential to the recently demonstrated hexagonal-ferrite super-lattice structures that are promising for room-temperature multiferroicity 41 , since the structural distortions in the h-LuFeO 3 layers are responsible for the ferroelectricity. The experimental characterization of strain effect in h-LuFeO 3 , can potentially be extended to measure the electronic and magnetic properties, when additional probes (e.g.…”