Converse magnetoelectric coupling in [(CH3)2NH2]Ni(HCOO)3 revealed by electron spin resonance

Electric-field (E) control of magnetism provides a direct route toward low power spin-based technologies by tuning magnetic states without current-driven dissipation. Here, we investigate converse magnetoelectric (CME) coupling in the multiferroic metal-organic framework [(CH3)2NH2]Ni(HCOO)3 (DMA-Ni-F) using electron spin resonance (ESR) as a microscopic probe of local spin environments and magnetic correlations. Temperature-dependent ESR spectra were recorded from 4.2 to 290 K under zero-field cooling (ZFC), electric-field cooling (EFC), and electric-magnetic-field cooling (EHFC), followed by in situ E-field application from +1.25 to −1.25 MV/m and reversed after EHFC. We demonstrate that EFC systematically suppresses the magnetic correlations across 4.2–290 K, evidenced by reduced double integral intensity (I) and broader peak-to-peak linewidth (ΔHpp) of EFC compared to ZFC, while the magnetic field (H) applied in EHFC suppressed the E-induced changes in spin dynamics. Notably, applying E after EHFC yields continuous and reversible modulation of I(E) and Hr(E) in the multiferroic state, providing microscopic evidence of CME coupling in DMA-Ni-F. The observed tunability is consistent with a well-established mechanism, where E-biased DMA+ dipolar configurations reorganize the N–H⋯O hydrogen-bond network and perturb the Ni–O–C–O–Ni chain, thereby modifying the local magnetic environment in the multiferroic DMA-Ni-F MOF.