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Room-temperature multiferroic and magnetodielectric properties of SrTiO3/NiFe2O4 composite ceramics
摘要： Various xNiFe2O4 ? (1-x)SrTiO3 (x = 0.04, 0.05, 0.1, 0.2) composite ceramics were prepared using sol–gel method and two-step calcination. The composite ceramics possessed no impurities and exhibited obvious magnetic properties (22.8 emu/g at x = 0.2). The magnetic second phase imposed strain effects on the SrTiO3 matrix to induce ferroelectricity. Strain values of (001) and (110) crystal planes were ~2.9% and ~1.3%. The tetragonal phase transition was evident in the Raman spectra. The remanent and maximum polarizations were 1.4 and 15.8 μC/cm2, respectively, in ceramic with 10 mol.% NiFe2O4. The dielectric permittivity was tuned with 1.6% change rate at 50 kHz and 10000 Oe.
关键词： Phase transition,Ferroelectricity,Strains,SrTiO3,Magnetodielectric
更新于2025-09-23 15:22:29
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Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping
摘要： The possibility of affecting the magnetic properties of a material by dielectric means, and vice versa, remains an attractive perspective for modern electronics and spintronics. Here, we report on epitaxial Bi(Fe0.5Mn0.5)O3 thin films with exceptionally low Gilbert damping and magnetoelectric coupling above room temperature (< 400 K). The ferromagnetic order, not observed in bulk, has been detected with a total magnetization of 0.44 μB/formula units with low Gilbert damping parameter (0.0034), both at room temperature. Additionally, a previously overlooked check-board ordering of oxygen vacancies is observed, providing insights on the magnetic and dielectric origin of the multifunctional properties of the films. Finally, intrinsic magnetodielectric behavior is observed as revealed by the variation of dielectric permittivity well above room temperature. These findings show the possibility of electric-field-controlled magnetic properties, in low Gilbert-damping-based spintronic devices, using single-phase multiferroic materials.
关键词： magnetodielectric,Gilbert damping,thin films,Bi(Fe0.5Mn0.5)O3,magnetoelectric coupling
更新于2025-09-11 14:15:04
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The origin of enhanced magnetodielectric effect in Y <sub/>3-x</sub> Yb <sub/>x</sub> Fe <sub/>5</sub> O <sub/>12</sub> ceramics
摘要： In this work, dielectric and magnetic behaviors, as well as magnetodielectric (MD) effect of Yb-substituted yttrium iron garnet (Y3-xYbxFe5O12) ceramics, have been studied systematically. Three dielectric relaxations are detected from the temperature spectrums, which can be attributed to the charge carries hopping between Fe2+ and Fe3+, inhomogeneous structure, and conduction, respectively. All the samples exhibit ferrimagnetic behaviors at room temperature and the saturation magnetization (Ms) increases ?rst and then decreases with increasing Yb-substitution. The variation of Ms can be viewed as a comprehensive effect of superexchange interaction of Fe1-O-Fe2 and double exchange interaction between Fe2+ and Fe3+ ions. The room-temperature MD effect of Y3-xYbxFe5O12 ceramics measured at 15 kOe and 1 MHz are ?1.11%, ?1.33%, ?2.04%, ?1.48%, and ?1.57%, for x = 0, 0.5, 1, 2, and 3, respectively. With the analysis of XPS spectra, the origin of enhanced MD effect has been investigated, and it is mainly caused by the response of local dipoles (Fe2+-Fe3+) under applied magnetic ?eld.
关键词： magnetodielectric effect,ferrimagnetic behaviors,Y3-xYbxFe5O12 ceramics,XPS spectra,dielectric relaxations
更新于2025-09-10 09:29:36
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Magnetodielectric effect in a metamaterial consisting of xerogel with embedded ε-Fe2O3 iron oxide nanoparticles
摘要： The ε-Fe2O3 iron oxide is a fairly rare polymorphic modification, which only exists in the form of nanoparticles embedded, as a rule, into a silica gel matrix. This magnetically ordered iron oxide, which exhibits a significant room-temperature coercivity, is a ferroelectric; therefore, the magnetoelectric and magnetodielectric properties of this material evoke keen interest. In this work, we investigate the magnetodielectric (MD) effect in a metamaterial consisting of xerogel SiO2 with embedded ε-Fe2O3 nanoparticles 9 nm in size on average in a concentration of 20 mass.%. This bulk material exhibits the MD effect in a wide temperature range. The temperature behavior of the permittivity is related to the magnetic state of the ε-Fe2O3 oxide, which undergoes the magnetic transition from the magnetically hard to magnetically soft phase in the temperature range of 80–150 K, indicating the interplay of the ε-Fe2O3 magnetic and charge subsystems.
关键词： ε-Fe2O3,magnetodielectric effect,xerogel,multiferroics,nanoparticles
更新于2025-09-04 15:30:14