Abstract
Magnetoelectric (Sr0.5Ba0.5Nb2O6)1−x−(CoFe2O4)x (x = 0.2–0.6) composites were prepared by a one-pot soft-chemistry synthesis using PEG400. Calcining at 700 °C resulted in nanocrystalline composite powders (dcryst. = 24–30 nm) which were sintered between 1050 and 1200 °C to ceramic bodies with relative densities up to 98%. SEM investigations confirm the formation of composite ceramics with a 0–3 connectivity and variable grain sizes from 0.2 to 3.6 μm for sintering up to 1150 °C, while sintering at 1200 °C leads both to a change in the microstructure and a considerable grain growth. Magnetic measurements at 300 K reveal ferrimagnetic behaviour with saturation magnetization values smaller than bulk CoFe2O4 and coercivities between 790 and 160 Oe. Temperature-dependent impedance spectroscopy showed that the relative permittivities decrease both with rising frequency and CoFe2O4 fraction. The frequency dependence of the impedance can be well described using a single RC circuit. Magnetoelectric measurements show the presence of pronounced field hystereses. The maximum magnetoelectric coefficient (αME) depends both on the CoFe2O4 fraction (x) and sintering temperature. The composite with x = 0.3 exhibits the largest αME value of 37 μV Oe−1 cm−1 (@ 900 Hz). With rising frequency of the AC driving field αME increases up to 300–400 Hz and is nearly constant until 1 kHz.
Highlights
Multiferroics, i.e. materials, which exhibit at least two ferroic orders are of special interest because of their potential applications as e.g. memories, actuators, spintronics, and sensors [1,2], because the coupling of order parameters results in new functionalities
We describe a straightforward one-pot soft-chemistry synthesis route using PEG400 to synthesize Sr0.5Ba0.5Nb2O6–CoFe2O4 composites with a 0–3 connectivity and with different CoFe2O4 molar fractions
A similar behaviour was found in BaTiO3–CoFe2O4, BaTiO3–Ni and Pb(Mg1/3Nb2/3)−PbTiO3–CoFe2O4 composites [36,37, 60,63]. This finding is in contrast to the one of Sutar et al [64] and Jigajeni et al [65] who observed a continuous increase of αME up to about 5 kHz in ferrite−strontium barium niobate composites
Summary
Multiferroics, i.e. materials, which exhibit at least two ferroic orders (e.g. ferromagnetism, ferroelectricity, and ferroelasticity) are of special interest because of their potential applications as e.g. memories, actuators, spintronics, and sensors [1,2], because the coupling of order parameters results in new functionalities. Multiferroic composites, consisting of a ferroelectric and a ferrimagnetic compound show strong ME effects at room temperatures which is mandatory for practical applications [7]. In such composite materials the coupling between the ferroic phases is mediated through the interface. Soft-chemistry routes, e.g. one-pot syntheses, lead to fine-grained powders which enable lower sintering temperatures resulting in ceramic bodies with tunable grain sizes [32,33]. Measurements of the magnetoelectric coupling were carried out depending on the magnetic DC field, frequency of the superimposed AC driving field, and temperature. The composite samples were characterized by magnetic measurements, impedance spectroscopy, and SEM
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
