[en] La_0.7Sr_0.3MnO₃ (LSMO) and SrFe₁₂O₁₉ (SFO) samples were synthesized by chemical coprecipitation method. The composites of (1 - x)LSMO:xSFO (x is mass%) were prepared using solid-state cosintering. The microstructure, electrical transport, and magnetic properties of the derived composites were systematically investigated. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) is observed in the composites. The magnetoresistance (MR) value at 300 K for the sample with x = 0.05 is about 2.9 times larger than that of the pure LSMO. The enhanced MR was attributed to the enhanced spin-dependent intergrain tunneling at the interfaces and grain boundaries due to the enhanced magnetic disorders and antiferromagnetic (AFM) couplings near boundaries between LSMO and SFO grains.

[en] Co_0.8Fe_2.2O₄ ferrite thin films have been prepared on Si(0 0 1) substrates by the chemical solution deposition. Structural characteristics indicate all films are single phase with spinel structure and the space group Fd3m-O_h⁷ and the mean grain size increases from 8 to 30 nm with the increase of annealing temperature. The magnetic properties of Co_0.8Fe_2.2O₄ thin films are highly dependent on annealing temperature. The sample annealed at 800 deg. C possesses high saturation magnetization, moderate coercivity and squareness ratio, making it a promising application candidate in high-density record and magneto-optical materials.

[en] La_0.7Sr_0.3MnO₃ nanoparticles were prepared by a simple chemical coprecipitation route. Structural, magnetoresistance (MR), and magnetic properties were investigated. Rietveld refinement of X-ray powder diffraction result shows that the sample is single-phase with the space group of R3-bar C. The result of field-emission scanning electronic microscopy shows that most of the grain sizes are distributed from 50 to 200 nm. The composition determined by energy-dispersive spectroscopy is the stoichiometry of La_0.7Sr_0.3MnO₃. The ferromagnetic to paramagnetic transition is sharp with Curie temperature T_C=367 K, which further confirms that the sample is single-phase. The steep change in MR at low fields is attributed to the alignment of the magnetization, while the high-field MR is due to the grain boundary effect.

[en] Polycrystalline CoFe_2O_4 thin films were deposited on Si (100) substrates by chemical solution deposition with and without magnetic annealing. Magnetic field directions were applied parallel and perpendicular to the film surface during the magnetic annealing process. The variations of strain, microstructure and magnetic anisotropy of the films caused by the magnetic annealing are investigated. The results show that the film densification is promoted and grain morphology is changed by the magnetic annealing, which can be attributed to the promoting effect of magnetization force on the grain growing and grain boundary diffusing. Magnetic measurements indicate the enhancement of anisotropy and saturation magnetizations of the polycrystalline CoFe_2O_4 after magnetic annealing. Furthermore, the rotation of easy axis along the field direction, the increased occupation of Co"2"+ ions at B sites and the additional strain induced by the magnetic field are considered as the main reasons of the increased magnetic anisotropy. - Highlights: • CFO films were annealed in magnetic field with parallel and vertical directions. • The film densification and grain size were changed by the applied magnetic field. • A higher saturation magnetization is obtained under magnetic annealing. • The enhanced magnetic anisotropy is observed after magnetic annealing

[en] M-type strontium hexaferrite (SrFe₁₂O₁₉) particles had been prepared by a modified chemical co-precipitation route. Structural and magnetic properties were systematically investigated. Rietveld refinement of X-ray powder diffraction results showed that the sample was single-phase with the space group of P6₃/mmc and cell parameter values of a=5.8751 A and c=23.0395 A. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 2 to 4 μm. The composition determined by energy dispersive spectroscopy is the stoichiometry of SrFe₁₂O₁₉. The ferrimagnetic to paramagnetic transition was sharp with Curie temperature T_C=737 K, which further confirmed that the samples were single phase. However, it was found that the coercivity, saturation magnetization and the squareness ratio of the synthesized SrFe₁₂O₁₉ samples were lower than the theoretical values, which could be explained by the multi-domain structure and the increase of the demagnetizing factor

[en] A Sr_0.8La_0.2Fe_11.8Co_0.2O₁₉ ferrite film has been prepared on a (0 0 1) sapphire substrate by chemical solution deposition. Structural characteristics indicate that the film is c-axis oriented and single-phase with space group P6₃/mmc. The grains are regular columnar with diameter between 50 and 100 nm as determined by atomic force microscopy. The sample possesses high saturation magnetization (130 emu/cm³), high coercivity (6.9 kOe), and large squareness ratio (0.9) at room temperature, which makes it a promising recording material.