Abstract
Revealing single-phase multiferroic (MF) materials in conventional bulk oxides is an exceptionally daunting task. However, achieving strong magnetoelectric (ME) coupling at room temperature (RT) in these materials is even more formidable despite their envisioned applications in multi-state memory storage devices, spintronics, magnetic field sensors, etc. The weak ME coupling in single-phase MF materials is primarily due to the ferro/antiferromagnetic ordering observed at very low temperatures, contrasting with ferroelectric ordering typically discerned at RT. These challenges can be effectively addressed by leveraging discrete molecular-based MF materials. Nonetheless, molecular-based ferroelectric materials remain in their infancy due to challenges in achieving polar point groups in these complexes. By overcoming these hurdles through meticulous molecular engineering, we have unveiled a discrete molecular complex, [CoIII3DyIII(L)6].4MeOH (Co3Dy), which exhibits an unprecedentedly strong ME coupling constant (α) value of 250 mVcm⁻¹Oe⁻¹ at RT. This robust ME coupling at or above RT presumably originates from the coupling between magnetostriction and ferroelectric phenomena observed in the paramagnetic Co3Dy complex. To demonstrate the ME coupling and harness the large α value, we have developed an ME nanogenerator device using Co3Dy to convert weak stray magnetic fields into electrical energy. This device produces an output voltage of ~ 430 mV and an output current of 0.3 µA under a small AC magnetic field amplitude of 24.2 Oe.