Large magnetoelectric effect and low-loss high relative permittivity in 0–3 CuO/PVDF composite films exhibiting unusual ferromagnetism at room temperature.

Flexible magnetoelectric 0–3 composite films formed with high dielectric (ε_r ∼ 10⁴) CuO microparticles in a polyvinylidene fluoride (PVDF) polymer matrix showed multifunctional properties. The films prepared by the hot-moulding technique exhibit low-loss high relative permittivity (ε_eff ∼ 10³) with good ferroelectric behaviour (with P–E loop) at the percolation threshold (f_CuO = f_c ∼ 0.25). Dielectric, ferroelectric, magnetic and direct magnetoelectric properties of the composites depend strongly on the CuO filler concentration (f_CuO). Interesting low field magnetoelectric response appears with about 5% decrease in ferroelectric polarization in the insulating composite (f_CuO = 0.20) along with 7.5% increase in the magnetodielectric coefficient under a magnetic field of 6 kG in the semiconducting percolative composite at room temperature. At this field, a maximum magnetoelectric voltage coefficient of 1.45 mV cm⁻¹ Oe⁻¹ was obtained. Even though the CuO sample is paramagnetic at ambient temperature, this typical composite film exhibits weakly ferromagnetic (with M–H loop) behaviour indicating multiferroic character. Our result represents an important step towards practical device applications using the high dielectric and magnetoelectric effects. [ABSTRACT FROM AUTHOR]