Recently, a research group led by Prof. Li Xiangyang from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS), theoretically predicted a series of multiferroic materials that can be applied in room-temperature environments by utilizing the d–p spin coupling combined with center-symmetry-breaking organic heterocycles in two-dimensional (2D) Cr-based metal-organic frameworks.
The research results were published in Nano Letters.
Multiferroic materials, characterized by the coexistence of two or three ferroic orders, have emerged as a pivotal research platform, driving advancements in information storage, sensing technologies, electronics, and energy conversion. The advent of 2D materials has revitalized the field of multiferroics, promising thinner, more efficient, and versatile functionalities. However, despite substantial strides in this area, the number of 2D multiferroics with room-temperature magnetism is still notably scarce.
To overcome this challenge, the researchers proposed a novel approach to achieve 2D room-temperature multiferroics in 2D metal-organic frameworks (MOFs) by leveraging the d-p spin coupling combined with center-symmetry-breaking six-membered heterocyclic ligands.
Using this method, they examined 128 different 2D MOFs and discovered three unique multiferroic materials: Cr(1,2-oxazine)2, Cr(1,2,4-triazine)2, and Cr(1,2,3,4-trazine)2. All of these materials exhibit ferrimagnetism as well as ferro/antiferroelectricity at room temperature. The room-temperature ferrimagnetic order is believed to originate from the strong d-p direct spin coupling between Cr cations and ligand anions.
Specifically, Cr(1,2-oxazine)2 displays ferroelectric characteristics, while the latter two exhibit antiferroelectric properties. Impressively, each of these materials possesses suitable barriers for polarization switching.
"Our study provided a promising platform for the design of 2D room-temperature multiferroic materials," said Prof. LI Xiangyang.
Schematic illustration of designing two-dimensional room-temperature multiferroic materials through d-p spin coupling and symmetry-breaking hexagonal heterocycles. (Image by Li Xiangyang)