title: Magnetoelectric coupling in the paramagnetic state of a metal-organic framework.
abstract: Although the magnetoelectric effects - the mutual control of electric polarization by magnetic fields and magnetism by electric fields, have been intensively studied in a large number of inorganic compounds and heterostructures, they have been rarely observed in organic materials. Here we demonstrate magnetoelectric coupling in a metal-organic framework [(CH3)2NH2]Mn(HCOO)3 which exhibits an order-disorder type of ferroelectricity below 185 K. The magnetic susceptibility starts to deviate from the Curie-Weiss law at the paraelectric-ferroelectric transition temperature, suggesting an enhancement of short-range magnetic correlation in the ferroelectric state. Electron spin resonance study further confirms that the magnetic state indeed changes following the ferroelectric phase transition. Inversely, the ferroelectric polarization can be improved by applying high magnetic fields. We interpret the magnetoelectric coupling in the paramagnetic state in the metal-organic framework as a consequence of the magnetoelastic effect that modifies both the superexchange interaction and the hydrogen bonding.
authors.affiliation: State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P R of China.
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: L-Q
authors.initials: LQ
authors.lastname: Yan
authors.forename: J-Z
authors.initials: JZ
authors.lastname: Cong
authors.forename: Y-L
authors.initials: YL
authors.lastname: Zhao
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: S-P
authors.initials: SP
authors.lastname: Shen
authors.forename: T
authors.initials: T
authors.lastname: Zou
authors.forename: D
authors.initials: D
authors.lastname: Zhang
authors.forename: S-G
authors.initials: SG
authors.lastname: Wang
authors.forename: X-F
authors.initials: XF
authors.lastname: Han
authors.forename: Y
authors.initials: Y
authors.lastname: Sun