Development of Co-Rich Microwires with Graded Magnetic Anisotropy

In this paper, a gradual change in the hysteresis loop of Co-rich glass-coated microwire stress-annealed at variable temperature is observed. Such microwires annealed with a temperature gradient also present a variable squareness ratio and magnetic anisotropy field along the microwire’s length. The obtained graded anisotropy has been attributed to a gradual modification of the domain structure along the microwire originated by a counterbalance between shape, magnetoelastic, and induced magnetic anisotropies. Accordingly, we propose a rather simple route to design graded magnetic anisotropy in a magnetic microwire.

Abstract P-7: NdFeCo-based Nanoparticles for Biomedical Applications

Background: The multifunctional nanoparticles can be promising antitumor materials. The results of a study of synthesized NdFeCoB oxide nanoparticles (NPs) as a basis for drug transportation systems are presented. In the next step, the NPs can be coated by a multifunctional gel shell. Methods: NPs, the composition of NdFexCo1-xB (where x =0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5), were synthesized by a Pechini-type sol-gel method. The synthesis allows tuning of NPs magnet properties by manipulating the microstructure and phase composition. NPs were studied by XRD, SEM, TEM, HRTEM, and VSM. Results: SEM images show that the average size of NPs changed from 280 nm (for x = 0) up to 416 nm (for x = 0.1 – 0.5). At TEM images the NPs of the sample without cobalt (x = 0) have an elongated shape (Fig 1a). Diffraction patterns showed that the NPs consist of single crystal or ordered crystallites. NPs with cobalt mainly consist of crystallites with a size of about 20-50 nm. There are also areas with a complex-grained microstructure. Hysteresis loops and first-order reversal curve analysis indicated that the NPs were ferromagnetic whose coercivity, squareness ratio, and magnetic interactions changed significantly with the cobalt contents.

Novel Molten Salt Assisted Autocombustion Method for the Synthesis of Aluminum-Doped SrFe12−xAlxO19 Hexaferrite Nanoparticles

The study presents a novel molten salt assisted autocombustion synthesis of SrFe12−xAlxO19 particles. The extrinsic magnetic properties such as coercivity and the remanence of sintered M-type ferrites are highly dependent on the microstructure viz. morphology and size, of the ferrite particles. The control of the microstructures of ferrite particles is usually achieved via control nucleation and grain growth process. In this study, NaCl salt was used to control the crystal shape and size of Al3+ doped SrFe12−xAlxO19 particles. The presented novel method couples advantage of deriving homogenized particles via auctocombustion first and later sintering in the presence of NaCl salt. Highly dispersed, homogeneous, and hexagonal shaped SrFe12−xAlxO19 ferrite particles were achieved with this method. The particles derived via the molten salt assisted method presented a high coercivity and squareness ratio (>0.5) as compared to that obtained via autocombustion method only.

Exchange-Coupling Behavior in SrFe12O19/La0.7Sr0.3MnO3 Nanocomposites

Magnetically hard-soft (100-x) SrFe12O19–x wt % La0.7Sr0.3MnO3 nanocomposites were synthesized via a one-pot auto-combustion technique using nitrate salts followed by heat treatment in air at 950 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM) were used to characterize the structural and magnetic properties of the samples. XRD spectra revealed the formation of a mixture of ferrite and magnetite phases without any trace of secondary phases in the composite. Microstructural images show the proximity grain growth of both phases. The room temperature hysteresis loops of the samples showed the presence of exchange-coupling between the hard and soft phases of the composite. Although saturation magnetization reduced by 41%, the squareness ratio and coercivity of the nanocomposite improved significantly up to 6.6% and 81.7%, respectively, at x = 40 wt % soft phase content in the nanocomposite. The enhancement in squareness ratio and coercivity could be attributed to the effective exchange-coupling interaction, while the reduction in saturation magnetization could be explained on the basis of atomic intermixing between phases in the system. Overall, these composite particles exhibited magnetically single-phase behavior. The adopted synthesis method is low cost and rapid and results in pure crystalline nanocomposite powder. This simple method is a promising way to tailor and enhance the magnetic properties of oxide-based hard-soft magnetic nanocomposites.