Hydrogen Bond Tuning of Magnetoelectric Coupling in Metal–Organic Frameworks

The
ordering of hydrogen bonds plays a vital role in breaking space
inversion symmetry and inducing the paraelectric to ferroelectric
phase transition in metal–organic frameworks (MOFs). Magnetic
field control of electric polarization has been observed in some MOFs.
However, little is known about the effect of hydrogen bonds on the
magnetoelectric effect in MOFs. Here, we studied the hydrogen bond
tuning of the magnetoelectric effect in the hybrid inorganic–organic
materials [(CH3)2NH2]­Mn­(HCOO)3 and [(CH3)2NH2]­Mn0.5Ni0.5(HCOO)3. Hydrogen bond energy is weakened
by the substitution of Ni ions in [(CH3)2NH2]­Mn­(HCOO)3, revealed by the dielectric measurement
and Raman spectra. Moreover, the hydrogen bond strength can tune the
contributions of the electric polarization components from the DMA+ cation and HCOO– framework, inducing the
positive and negative magnetoelectric coefficients in [(CH3)2NH2]­Mn­(HCOO)3 and [(CH3)2NH2]­Mn0.5Ni0.5(HCOO)3, respectively. Our study gives a microscopic mechanism for
understanding the hydrogen bond assisted magnetoelectric effect.