Linear magnetic field dependence of the magnetodielectric effect in eutectic BaTiO3-CoFe2O4 multiferroic material fabricated by containerless processing

Abstract

To maximize the formation of an anisotropic interface between the magnetostrictive phase and the electrostrictive phase, a eutectic BaTiO3-CoFe2O4 multiferroic material is fabricated by containerless processing. The composites in this process had a fine eutectic structure, especially at a eutectic composition of BaTiO3:CoFe2O4 = 62:38. TEM observations revealed that the (1 0 0) plane of tetragonal BaTiO3 and the (1 0 0) plane of CoFe2O4 were oriented in parallel. In addition to the largest magnetodielectric effect in the eutectic-composition samples, we confirmed the permittivity is controlled linearly by applying a high magnetic field through forced magnetostriction. So far, the peak of the magnetodielectric effect around 0.25 T has been only found in the sintered CoFe2O4 polycrystalline sample. Thus, the containerless processing provides us a route to produce an ideal microstructure without accompanying 90° domain wall process and rotational magnetization process, which enhances the magnetodielectric effect.

Low-magnetic-field controlled magnetodielectric coupling at room temperature in a chiral layered diphenylalanine-based 1D-coordination-polymer

“…The di electric constants for E // [0 0 1] and H// [0 0 1] are suppressed strongly even in low magnetic field up to room temperature in figure 4(c). The MD coefficients (MD = [ε′(H) − ε′(0)]/ε′(0) = Δε′/ε′(0)) [32,33] starts to increase sharply at 125 K, and reach their maximums at ~288 K. The largest MD value at 288 K and 0.5 T reaches ~ − 22.4%. Then, the MD coefficient begins to decrease slowly upon increasing temperature.…”

“…The spin magnetic moments in paramagnetic state can easily be aligned even under low-magnetic-field. Therefore, the susceptibility of dipoles nearby should be suppressed by the alignment of spin magnetic moments through the spin-lattice coupling, which can suppress the dielectric constant and cause the strong MD effect [5,17,33]. Then, we attempted to measure the magnetoresistance to detect the extrinsic contribution to the di electric relaxations.…”

Synthesis of functional ceramics by microwave non-equilibrium processing

“…Furthermore, during rapid heating in the microwave process, the PVP coated on the raw TiO 2 powder behaves differently in terms of melting, decomposition, and carbonization than when heated in an electric furnace. 33) The heating rate of the electric furnace was 5 °C/min, resulting in a long time from melting to carbonization of PVP and aggregation of the raw TiO 2 nanoparticles/nanorods. In contrast, in the microwave process, the time from melting to decomposition of PVP was as short as 66 s. Therefore, the carbonization of PVP proceeds while the nanorods are uniformly dispersed in PVP, and a uniform carbon coating is considered to have been formed.…”

Epitaxial Growth of Orthorhombic GaFeO3 Thin Films on SrTiO3 (111) Substrates by Simple Sol-Gel Method

“…Multiferroic materials possessing magnetic and electric properties simultaneously in the single phase, supply a favorable method to design new devices with high performance. With the coupling of these two properties, these materials show interesting physics such as ferroelectric properties that can be changed by magnetic fields and ferromagnetic properties that can be controlled by electric field [1,2,3,4]. Multiferroic materials can be applied in the development of new devices like sensors [5,6,7], transducers [8,9], second harmonic generation [10] and information storage [11,12,13].…”