Junzhuang Cong

Magnetoelectric coupling in the paramagnetic state of a metal-organic framework

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.

Observation of Resonant Quantum Magnetoelectric Effect in a Multiferroic Metal-Organic Framework.

A resonant quantum magnetoelectric coupling effect has been demonstrated in the multiferroic metal-organic framework of [(CH3)2NH2]Fe(HCOO)3. This material shows a coexistence of a spin-canted antiferromagnetic order and ferroelectricity as well as clear magnetoelectric coupling below TN ≈ 19 K. In addition, a component of single-ion quantum magnets develops below ∼ 8 K because of an intrinsic magnetic phase separation. The stair-shaped magnetic hysteresis loop at 2 K signals resonant quantum tunneling of magnetization. Meanwhile, the magnetic field dependence of dielectric permittivity exhibits sharp peaks just at the critical tunneling fields, evidencing the occurrence of resonant quantum magnetoelectric coupling effect. This resonant effect enables a simple electrical detection of quantum tunneling of magnetization.

Magnetic-ion-induced displacive electric polarization inFeO5bipyramidal units of(Ba,Sr)Fe12O19hexaferrites

Electric polarization in conventional ferroelectric oxides usually involves nonmagnetic transition-metal ions with an empty d shell (the d

Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba1.3Sr0.7Co0.9Zn1.1Fe10.8Al1.2O22

^0

Interface-modification-enhanced tunnel electroresistance in multiferroic tunnel junctions

rule). Here we unravel a new mechanism for local electric dipoles based on magnetic Fe

Nonvolatile Memory Based on Nonlinear Magnetoelectric Effects

^{3+}

Giant exchange bias in a single-phase magnet with two magnetic sublattices

(3d

Nonvolatile transtance change random access memory based on magnetoelectric P(VDF-TrFE)/Metglas heterostructures

^5

A multilevel nonvolatile magnetoelectric memory

) ion violating the d

Large pyroelectric and thermal expansion coefficients in the [(CH3)2NH2]Mn (HCOO)3 metal-organic framework

^0