Electric-Field Modulation of Spin Resonance in a Perovskite-Like Multiferroic Fe–Metal–Organic Framework

Electric-field (E) modulation of magnetic order in hybrid materials remains of significant interest for multiferroic metal–organic frameworks. Here, we investigated the spin-resonance response of single-crystal [(CH3)2NH2]Fe(HCOO)3 (Fe-MOF) via X-band electron spin resonance (ESR) under four cooling conditions, including zero-field cooling (ZFC), magnetic-field cooling (HFC), electric-field cooling (EFC), and combined electric- and magnetic-field cooling (EHFC). These measurements revealed protocol-dependent variations in the resonance field (Hr) and double-integral intensity (I) within the magnetically ordered phase below ∼18.5 K (TN). After EFC, E variation from 0 to 2.2 MV/m and back produced small but reproducible Hr shifts (ΔHr ≈ 0.3 mT) and systematic I(E) variations. While under EHFC, E variation from +2.2 to −2.2 MV/m and back produced a larger symmetric modulation (ΔHr ≈ 1.2 mT) and reversible I(E) changes. The electric-field response decreased progressively with increasing temperature, and it became negligible at TN, indicating that the effect was confined to the magnetically ordered phase. These results demonstrated electric-field sensitivity of the resonance response, consistent with dipole-coupled spin interactions in the framework.