Structural phase transitions as the overlooked key to boost the electric response in multiferroic composites

The convergence of pyroelectric (PE) and magnetoelectric (ME) technologies presents a transformative opportunity for advancing key areas of our increasingly digitized society, ranging from next-generation sensors and spintronic voltage control to highly efficient energy harvesting systems. In this study, we explore the synergistic effects of combining P(VDF-TrFE) piezopolymer with Ni–Mn–Ga magnetic shape memory alloy fillers. Our experimental results reveal a 2.5-fold increase in the PE coefficient due to the cubic-tetragonal phase transition of Ni–Mn–Ga particles, dramatically enhancing the intrinsic properties of the piezopolymer. Theoretical modeling confirms that this increase is driven by the mechanical stress imparted by the phase transition within the composite material. Moreover, the ME response under cyclic temperature variation (from 298 to 328 K) demonstrates an unprecedented leap, with the ME coefficient surging from 4.3 V cm ‒1 Oe ‒1 to 20 V cm ‒1 Oe ‒1 during narrow 2 K intervals, attributed to phase transitions in the Ni–Mn–Ga filler. Remarkably, even the lowest observed ME coefficient exceeds by two orders of magnitude the maximum reported for similar P(VDF-TrFE)-based composites, signaling a breakthrough in polymer-based ME materials. These findings open new horizons for future technological innovation, where the manipulation of structural phase transitions in composite materials can unlock extraordinary advancements in multifunctional devices. The significant leap in PE and ME performance underscores the potential for disruptive applications in energy, sensing, and spintronics.