Resonant Quantum Magnetodielectric Effect in Multiferroic Metal–Organic Framework [CH₃NH₃]Co(HCOO)₃

Abstract The observation of both resonant quantum tunneling of magnetization (RQTM) and resonant quantum magnetodielectric (RQMD) effect in the perovskite multiferroic metal–organic framework [CH₃NH₃]Co(HCOO)₃.is reported. An intrinsic magnetic phase separation emerges at low temperatures due to the hydrogen‐bond‐modified long‐range super‐exchange interaction, leading to the coexistence of canted antiferromagnetic order and single‐ion (Co²⁺) magnets. Subsequently, a stair‐shaped magnetic hysteresis loop along the [101] direction characterizing the RQTM appears below the magnetic blocking temperature. More interestingly, the magnetic field dependence of dielectric permittivity exhibits pronounced peaks at the critical fields corresponding to the RQTM, a phenomenon termed the RQMD effect which enables electrical detection of the RQTM. The magnetostriction shows a similar behavior to the magnetodielectric effect at 2 and 5 K, which suggests that the magnetodielectric effect in this multiferroic metal–organic framework is related to the spin‐lattice coupling.