•MnO@MWCNTs composite films with porous structure are prepared by ESD technique.•The sample shows good cycling performance of 588 mAh g−1 after 100 cycles at 1 C.•MnO@MWCNTs composite anode exhibits high rate capability of 424 mAh g−1 at 5 C.•We provide a way to prepare composite anode materials for the lithium-ion battery.MnO@multi-walled CNTs (MnO@MWCNTs) composite film electrodes with porous structure are synthesized by the improved electrostatic spray deposition (ESD) setup. The content of 5.47 wt% MWCNTs is found to be optimal, which can improve the conductivities of MnO film electrodes without destroying their porous structure and obtain good cycling performance (588 mAh g−1 after 100 cycles at 1 C) and high rate capabilities (424 mAh g−1 at 5 C). The effects of MWCNTs on the morphology of the electrodes and the electrochemical performances have been studied. It is found that the electrostatic repulsion between the charged spray droplets can be remarkably reduced by excessive adding MWCNTs, which leads to the breakdown of the 3D porous morphology of the MnO film electrodes and the electrochemical performance becomes worse.

The magnetic field-induced acceleration of the Ostwald ripening process was demonstrated firstly in the formation of hollow Fe3O4 nanospheres. Similar to the maintaining time, the magnetic field can act as an independent parameter to control the crystallite size, hollow structure, and pore size of nanostructures in the Ostwald ripening process.

•BaTiO3–CoFe2O4 multilayer films with different thickness were prepared.•Grain size, grain boundary and strain can be regulated by magnetic annealing.•Ferroelectric and dielectric properties are improved by magnetic annealing.•Leakage current densities are decreased after magnetic annealing.•The thinner the films, the more significant the magnetic annealing effect.BaTiO3–CoFe2O4 multilayer thin films with different thickness are deposited on Pt/Ti/SiO2/Si (100) substrates via CSD method. The magnetic annealing effect on the ferroelectric and dielectric properties of the multilayer thin films are investigated. It is found that both the ferroelectric and dielectric properties of the films are improved by the magnetic annealing. The changes of these two properties can be explained based on the variations of grain size, grain boundary, internal stress/strain as well as domain wall motion. A serial capacitor model is also used to analyze the influence of magnetic annealing on the dielectric properties. Leakage current densities are decreased after magnetic annealing and then fitted and explained with different leakage conduction mechanisms. Finally, comparing the ferroelectric and dielectric properties of the films with and without magnetic annealing, it can be concluded that the magnetic annealing effect is more significant on the thinner films.

•First report systematically the magnetism of Mg-doped Ba0.5Sr1.5Zn2Fe12O22.•The range for intermediate-III phase increases significantly as x increases to 2.0.•Magnetic-field-induced ferroelectric phase can be stabilized at 0 T by Mg2+.The microstructure and magnetic properties of Mg-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the solid state method are investigated. All the undoped and doped samples show a sharp screw proper spin phase to collinear ferrimagnetic spin phase transition above room temperature, and transition temperature increases distinctly with Mg doping. It is noteworthy that all the samples exhibit another magnetic phase transition at a lower temperature T1, which is associated with the longitudinal conical to the proper screw phase transition. The transition temperature T1 can be modulated by varying Mg content, indicating that the longitudinal conical spin phase is stabilized by the Mg-substitution. The saturation magnetization at room temperature increases to a maximum with Mg content x = 0.8 and then decreases with x. The variations of magnetic properties can be ascribed to the difference in the preferential site for Zn and Mg and different distribution of Fe3+ ions over tetrahedral and octahedral sites. It is worth noting that the range for the intermediate-III phase increases significantly as x increases to 2.0, suggesting that Mg-doped samples may be display field-induced ferroelectric order at temperature close to RT and in wide magnetic-field regions. The room-temperature M-H curves at lower applied field indicate that magnetic-field-induced ferroelectric phase can be stabilized at zero magnetic field by the substitution by Mg2+ for Zn2+. The Mg-doped hexaferrites Ba0.5Sr1.5Zn2Fe12O22 may be potential candidates for applying in magnetoelectric devices.

•La0.7Sr0.3MnO3 (LSMO) films were synthesized by chemical solution deposition.•Under the external magnetic field, the grains of LSMO films grow larger.•The saturation magnetization and Curie temperature are obviously enhanced during the magnetic-field annealing.•The enhanced magnetic properties are reasonably explained.The chemical solution deposition was used to synthesize La0.7Sr0.3MnO3 (LSMO) films. Effects of external magnetic-field (Hext=5 kOe) annealing on microstructure and magnetic properties were investigated. Under the effect of external magnetic field, FE-SEM images indicate that the mean grain size of LSMO film increases. X-ray diffraction results show that all the LSMO films are single-phase rhombohedral structure with a space group of R3¯C. The coercivity (Hc) of the magnetic-field annealing LSMO film decreases slightly. The values of Curie temperature (TC) and saturation magnetization (Ms) are obviously enhanced, which can be explained by the influence of the magnetic texture and enlarged grain size.

The magnetic and magnetocaloric effect (MCE) of Mg or Cu-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the sol-gel method are investigated. The Ba0.5Sr1.5Zn2Fe12O22 shows a sharp paramagnetic to ferrimagnetic phase transition and a large conventional MCE at around room temperature. By the partial substitution of Zn with Mg or Cu, the magnetic transition temperature as well as the maximum MCE temperature can be tuned in the range of 300 and 375 K while keeping the maximum MCE nearly unchanged, which are beneficial characteristics for their application as near room-temperature magnetic refrigerants. For Ba0.5Sr1.5Zn2Fe12O22, it is found that the maximum values of magnetic entropy change –ΔSM and relative cooling power (RCP) are 1.27 J/kg K and 124 J/kg for ΔH=4.4 T, respectively. Given its advantages, such as large RCP, suitable working temperature, low-cost raw materials, easy to synthesize, and environment-friendly, the Ba0.5Sr1.5Zn2Fe12O22 related hexaferrites may be potential candidates for room-temperature magnetic refrigeration.

The n = 5 Aurivillius phase ceramics Bi6Fe2−xMnxTi3O18 (BFMTO) (0 ≤ x ≤ 0.8) were synthesized with a conventional solid-state reaction method. All samples can be indexed with an orthorhombic structure with the space group B2cb. The magnetic measurements indicate that these ceramics are predominantly paramagnetic with the presence of short-range antiferromagnetic interactions and a weak ferromagnetic ordering state, implying that the predicted Fe3+–O–Mn3+ 180° ferromagnetic superexchange interaction based on the Goodenough–Kanamori rule might not be achieved in BFMTO ceramics through Mn substitution for Fe in the n = 5 Aurivillius phase. The dielectric loss of the x = 0.3 and 0.4 samples demonstrates the relaxation process and the rather large activation energy (2.63 eV for the x = 0.3 sample and 2.10 eV for the x = 0.4 sample) implies that this relaxation process is not due to the thermal motion of oxygen vacancies. The 0.5 ≤ x ≤ 0.8 samples exhibit a paraelectric–ferroelectric phase transition and the ferroelectric Curie temperature decreases upon increasing the doping level of Mn.

Carbonyls iron powders (CIPs)/Fe3O4 composites have been prepared by a simple hydrothermal method through controlling the pH value of the reaction system. The obtained products were characterized by X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM), superconducting quantum interference device magnetometer (SQUID), thermogravimetry–differential thermal analysis (TG–DTA), etc. The microwave absorption properties of the CIP/Fe3O4 composites were measured by vector network analysis (VNA). A wide region of microwave absorption was achieved due to the high permeability of CIP/Fe3O4 composites (pH = 13). When the matching thickness is 2 mm, the reflection loss of the sample exceeding −10 dB was obtained at the frequency range of 8.7–15.0 GHz, with an optimal reflection loss of about −38.1 dB at 11.5 GHz. A possible mechanism of the improved microwave absorption properties of the composites was discussed.Highlights► Higher imaginary part of the complex permeability and higher electric resistivity achieved because of the ferromagnetic property of Fe3O4. ► The reflection loss of the sample exceeding −10 dB was obtained at the frequency range of 8.7–15.0 GHz. ► The optimal reflection loss of −38.1 dB was achieved at 11.5 GHz for the thickness of 2.0 mm.

Ni1−xZnxFe2O4 (0⩽x⩽1, in steps of 0.1) nanocrystallines were synthesized by sol-gel route. The doping effects of zinc on structural, magnetic and microwave absorption properties were investigated in detail. X-ray diffraction (XRD) results show that all the samples are single-phase spinel structure. The magnetic and microwave absorption properties are strongly dependent on the zinc content, which can be understood in terms of the cations redistribution in spinel tetrahedral and octahedral sites with the increase of zinc content. The magnetic measurement shows the antiferromagnetic nature of the samples for x=0.9 and x=1.0. The saturation magnetization reaches the maximum of 3.35 μB/f.u. at x=0.5. The optimal reflection loss (RL) of −29.6 dB is found at 6.5 GHz for an absorber thickness of 5 mm. The RL values exceeding −10 dB are obtained for the absorber in the range of 3.9–8.9 GHz. These Ni1−xZnxFe2O4 nanocrystallines may be attractive candidates for electromagnetic wave absorption materials.

M-type barium hexaferrites Ba1−xCexFe12−xCoxO19 (0.0≤x≤0.30.0≤x≤0.3) have been synthesized by a simple chemical coprecipitation method. X-ray diffraction (XRD) studies indicate that the samples are of single phase, with space group P63/mmcP63/mmc. The results of field-emission scanning electronic microscopy (FE-SEM) show that the grains are regular hexagonal platelets with sizes from 0.5 to 1.5μm. It is observed that the value of the coercivity field (HcHc) increases at low substitution (x≤0.1x≤0.1), reaches a maximum at x=0.1x=0.1, and then decreases at x≥0.1x≥0.1, while the value of saturation magnetization (MsMs) decreases monotonically with increasing xx. The variations of magnetic properties can be tentatively attributed to the effects of Ce–Co substitution. The results above indicate that our samples might be promising candidates for permanent magnets and perpendicular recording media materials in the future.Highlights► The grains of BCFCO ferrites are regular hexagonal platelets with sizes between 0.5 and 1.5μm. ►TCTC shifts to lower temperature with increasing Ce–Co substitution level. ► Samples exhibit decreased saturation magnetization (MsMs) values with increasing xx. ►HcHc increases at x≤0.1x≤0.1, and then decreases at x≥0.1x≥0.1.

In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO3/CoFe2O4 bilayered by chemical solution deposition route are investigated. It is observed that magnetic annealing can enhance the crystallization quality, texture and densification as well as dielectric properties. In addition, the magnetolosses decrease with increasing the magnetic fields. Moreover, both increase of the polarization and decrease of the leakage current due to magnetic annealing are beneficial for potential applications of BiFeO3 films.Research highlights► Enhanced c-axis oriented BFO/CFO bilayered thin films were prepared via magnetic annealing. ► It is observed that, the polarization and leakage current of the bilayered thin films increases and decreases respective with the magnetic annealing, which is very useful for applications.

The intrinsically core/shell structured La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores have been prepared. The magnetic, dielectric and microwave absorption properties are investigated in the frequency range from 1 to 12 GHz. An optimal reflection loss of −41.1 dB is reached at 8.2 GHz with a matching thickness of 2.2 mm, the bandwidth with a reflection loss less than −10 dB is obtained in the 5.5–11.3 GHz range for absorber thicknesses of 1.5–2.5 mm. The excellent microwave absorption properties are a consequence of the better electromagnetic matching due to the existence of the protective amorphous shells, the ferromagnetic cores, as well as the particular core/shell microstructure. As a result, the La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores may become attractive candidates for the new types of electromagnetic wave absorption materials.