High frequency magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles

Abstract

Magneto-dielectric effects in self-assembled core-shell nanoparticles of nickel ferrite (NFO) and barium titanate (BTO) have been investigated in the millimeter wave frequencies. The core-shell nano-composites were synthesized by coating 100 nm nickel ferrite and 50 nm barium titanate nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst forming heterogeneous nanocomposites. Magneto-electric (ME) characterization of as-assembled particles has been carried out by measurements of the relative permittivity ɛr as a function of frequency f under an applied static magnetic field H over 16–24 GHz. Measurements show an H-induced decrease in ɛr of 1 to 1.5%. But a giant magneto-dielectric effect with an H-induced change in permittivity as high as 28% is measured under dielectric resonance in the samples. A strong ME coupling was also evident from H-tuning of dielectric resonance in the composites. A theory for the high frequency magneto-dielectric effect has been developed and consists of the following steps. First the Bruggeman model is used to estimate the effective dielectric constant for the shell consisting of the BTO particles and voids considered as spherical air-pores. Then the permittivity for the core and shell is estimated taking into consideration the sample porosity. Finally the H-dependence of the permittivity due to ME interactions is calculated from the free energy considerations. Estimated ɛr vs. H and dielectric resonance frequency vs. H characteristics are in general agreement with the data.

Technobiology’s Enabler: The Magnetoelectric Nanoparticle

“…In fact, it could be substantially increased (by orders of magnitude) at a frequency corresponding to a natural resonance, whether the resonance is the result of mechanical vibrations, ferromagnetic precession, or a combination of the two or not (Yu et al 2008). Ideally, the highest resonance would take place when both phases, magnetic and electric components, respectively, resonate at the same frequency (Popov et al 2014). However, most of these resonances in such small nanostructures typically occur in a GHz range (e.g., from below 5 to over 10 GHz).…”

Theory of magnetoelectric effects in multiferroic core–shell nanofibers of hexagonal ferrites and ferroelectrics

“…The fibers were assembled into 2D and 3D films with magnetic and/or electric fields [23]. Strong ME interactions in core-shell particles and coaxial wires were evident from measurements of the low-frequency ME effect, magnetic field induced polarization, and magnetodielectric effects at 1-40 GHz [17,23,24].…”

Realization of Enhanced Magnetoelectric Coupling and Raman Spectroscopic Signatures in 0–0 Type Hybrid Multiferroic Core–Shell Geometric Nanostructures

“…The voltage control of magnetism, exhibited by multiferroics, makes them attractive and promising for multifunctional device applications. − Hence, the exploration of hybrid multiferroic materials or artificial multiferroics in which ferromagnetism and ferroelectricity coexist is highly appealing and of great technological significance. − Multiferroic materials are rare in nature − and of great demand due to their potential to conserve power and space and their amazing applications in information technology, data storage, magnetoelectric sensors, multiple-state memories, , and emerging ultralow-power spintronics technology. − The electromagnons , or the quantized hybrid spin–lattice excitations in multiferroics , have opened up vast doors in the emerging magnonic and spintronics technology and production of fast, reliable, and low power magnetoelectric devices.…”