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

Electric-field () 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 [(CH)NH]Fe(HCOO) (Fe-MOF) via X-band electron spin resonance (ESR) under four cooling conditions, including zero-field cooling (), magnetic-field cooling (), electric-field cooling (), and combined electric- and magnetic-field cooling (). These measurements revealed protocol-dependent variations in the resonance field () and double-integral intensity () within the magnetically ordered phase below ∼18.5 K (). After , variation from 0 to 2.2 MV/m and back produced small but reproducible shifts (Δ ≈ 0.3 mT) and systematic () variations. While under variation from +2.2 to -2.2 MV/m and back produced a larger symmetric modulation (Δ ≈ 1.2 mT) and reversible () changes. The electric-field response decreased progressively with increasing temperature, and it became negligible at , 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.