Towards room-temperature and above magnetoelectricity in CoFe₂O₄/Cr₂O₃ core/shell nanoparticles

Abstract

This work provides an effective approach to increase the magnetoelectric (ME) operating temperature of primordial sesqui oxide Cr2O3. The CoFe2O4 (core)/Cr2O3 (shell) nanoparticles with varying molar fractions are prepared via the sol-gel auto-combustion method. The phase-purity and coating induced micro-strains in core as well as shell have been validated from the Rietveld refinement of X-ray diffraction data, and are complementary to the Fourier transform infrared spectroscopy and Raman spectroscopy studies. Transmission electron microscopy measurement confirms the core/shell configuration of the nanoparticles. The magnetization measurements suggest screening of ferromagnetic interaction of CoFe2O4 (core) due to Cr2O3 shell over it, such that core/shell nanoparticles respond like single domain particles. A careful inspection of the impedance and modulus data suggest single relaxation in the studied frequency/temperature range for all the compositions. Both, the relaxation and the conduction processes are found to be polaronic obeying Mott variable range hopping mechanism. Direct ME measurements on these samples manifests the presence of linear magnetoelectricity for temperature as high as 400 K ―a hallmark of enhancement in ME operating temperature of parental Cr2O3 phase and therefore widen its scope to meet the necessity of ME based potential applications.

Manganese substitution induced magnetic transformation and magnetoelectricity in SrFe12O19

“…The 2 β / d contribution to ME is extracted from the data (which may also be having magnetoloss contribution 52,57 ) by fitting it via eqn (6).where, σ / d is related to the magnetoconductivity/magnetoloss effect. The substitution of Mn has increased the σ / d (in mV × cm −1 × Oe −3 ) gradually; at room temperature ∼10 −6 (SrM), 0.01(4) × 10 −3 (SrM3), 0.05(4) × 10 −3 (SrM5), 1.01(3) × 10 −3 (SrM7).…”

“…The 2b/d contribution to ME is extracted from the data (which may also be having magnetoloss contribution 52,57 ) by fitting it via eqn (6).…”

Energy-Harvesting Performance in a LaYFe2O6/P(VDF-HFP) Nanocomposite by Boosting the Magnetoelectric Effect

“…To capture the maximum magnetic field produced by the current-carrying power cable, the device is kept just below the cable (Figure d). From the impedance spectroscopy measurement, the internal impedance of the MENG is estimated ( Z ∼ 6.28 × 10 6 Ω at 100 Hz). Figure f shows the Cole–Cole plot of impedance, from which the impedance of the device ( Z = R e false[ Z false] 2 + I m false[ Z false] 2 ) is calculated as a function of the frequency (upper inset of Figure f).…”

“…From the impedance spectroscopy measurement, the internal impedance of the MENG is estimated ( Z ∼ 6.28 × 10 6 Ω at 100 Hz). Figure f shows the Cole–Cole plot of impedance, from which the impedance of the device ( Z = R e false[ Z false] 2 + I m false[ Z false] 2 ) is calculated as a function of the frequency (upper inset of Figure f). However, the output power density so calculated by using the internal impedance of the device is ∼0.5 μW cm –3 .…”