Two-dimensional hyperferroelectric metals: A different route to ferromagnetic-ferroelectric multiferroics

Wei Luo, Ke Xu, and Hongjun Xiang
Phys. Rev. B 96, 235415 – Published 11 December 2017
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Abstract

Recently, two-dimensional (2D) multiferroics have attracted a lot of attention due to their fascinating properties and promising applications. Although the ferroelectric (FE)-ferroelastic and ferromagnetic (FM)-ferroelastic multiferroics have been observed/predicted in 2D systems, 2D ferromagnetic-ferroelectric (FM-FE) multiferroics remain to be discovered since FM insulators are very rare. Here we proposed the concept of 2D hyperferroelectric metals, with which the insulating prerequisite for the FM-FE multiferroic is no longer required in 2D systems. We validate the concept of 2D hyperferroelectric metals and 2D metallic FM-FE multiferroics by performing first-principle calculations on 2D CrN and CrB2 systems. The 2D buckled monolayer CrN is found to be a hyperferroelectic metal with the FM ground state, i.e., a 2D FM-FE multiferroic. With the global optimization approach, we find the 2D CrB2 system has an antiferromagnetic (AFM)/planar ground state and a FM/FE metastable state, suggesting that it can be used to realize electric field control of magnetism. Our analysis demonstrates that the spin-phonon coupling and metal-metal interaction are two mechanisms for stabilizing the out-of-plane electric polarization in 2D systems. Our work not only extends the concept of FE to metallic systems, but also paves a way to search the long-sought high temperature FM-FE multiferroics.

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  • Received 23 April 2017
  • Revised 25 September 2017

DOI:https://doi.org/10.1103/PhysRevB.96.235415

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Wei Luo1,2, Ke Xu1,2,3, and Hongjun Xiang1,2,*

  • 1Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
  • 2Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
  • 3Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, 441053, People's Republic of China

  • *hxiang@fudan.edu.cn

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Issue

Vol. 96, Iss. 23 — 15 December 2017

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