Probing the magnetic domain interaction and magnetocapacitance in PVDF – (nickel–cobalt–manganese ferrite)@barium titanate core–shell flexible nanocomposites

Abstract

In this paper, we report a facile method to synthesize Ni_0.93Co_0.02Mn_0.05Fe_1.95O_4−δ (NCMF)@BaTiO₃ (BT) core–shell nanoparticles. Flexible thick films of polyvinylidene fluoride (PVDF)-NCMF@BT core–shell nanocomposites with a thickness ∼110 μm were developed. We analysed the impact of the BT shell phase on the magnetic domain distribution and its interaction on the final properties of the composites. The magnetic force microscopy (MFM) microstructure revealed well confined, highly dense, and isolated nanodomains of NCMF. The adequate isolation provided by the BT encapsulation highly reduced the potential of charge leakage among the neighbouring NCMF nanoparticles, and hence, the dielectric loss. Their magnetodielectric measurements demonstrated good sensing performance even at a modest magnetic field of 100 Oe. At 1 kHz, significant magnetocapacitance (M_C) and magnetoresistance (M_R) values of 1.7% and −4.2% were achieved at 100 Oe and these values increased to a maximum of 4.9% and −10.8% at 1000 Oe for PVDF-50 vol% of the NCMF@BT nanopowder composite, respectively, making them a promising candidate for advanced magnetically ordered pseudocapacitive materials in energy storage in supercapacitor applications.