Effect of chromium substituted on structural and magnetic characterization lithium ferrite nanoparticles

In this work, we present a structural, morphology and magnetic study of the Li0.5Fe2.5-xCrxO4 spinel nanoparticles (x = 0, 0.5, 0.75, 1, and 1.25) with mean particle size of 20-30 nm prepared by sol-gel method. The lattice constants and the size of particle decrease with increasing Cr concentration. In these samples, the preference of Cr3+ and Li+ ions in the octahedral sites and a small degree of site-interchange between Li+ in the octahedral sites and Fe3+ in the tetrahedral sites were found which increases with increasing the Cr content. A decrease of magnetization due to the spin disorder in the surface layer of the particles was observed. The spontaneous magnetization at 5K suggests the Néel type of magnetic ordering in these samples. The magnetic coercivity is discussed in terms of particle size, morphology and chromium substitution. Keywords. Chromium substitution, sol-gel method, nanoparticles, lithium ferrite

Enhancement of Magnetic Properties of La-substituted Strontium Hexaferrite Particles Prepared by Sol-gel Route

La-substituted strontium hexaferrite particles Sr$_{1 - x}$La$_{x}$Fe$_{12}O_{19}$ $(x = 0 \div 0.2)$ were prepared by using sol-gel method and subsequent calcination at temperatures ranging from 750\rc{}C to 1050\rc{}C for 2h in air. The effects of the initial La concentration and the calcination temperature on the structure, particle morphology and magnetic properties of the hexaferrite samples were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The high magnetic coercivity $(_{i}H_{c}$) of 6.6 - 6.7 kOe and magnetization in maximum applied magnetic field (13.5 kOe) of 68 - 72 emu/g were achieved with the particles of compositions x = 0.1 $\div$ 0.2 and calcination temperatures between 850\rc{}C and 1000\rc{}C. The experimental data indicate that La replacement for Sr improves the crystallinity and inhibits the grain growth of the samples in a wide range of calcination temperature. These factors are important for production of high-coercivity hexaferrites by sol-gel technology

The influence of Tantalum content in relation to substrate temperature on magnetic and structural properties of Co-Cr-Ta thin films

In this study, we investigated the influence of Ta content (in Co86Cr12Ta2 and Co82Cr13Ta5 compositions) on magnetic and structural properties of Co–Cr–Ta perpendicular media samples grown on Si substrates at different substrate temperatures during RF-sputter deposition. In general, coercivity of Co82Cr13Ta5 samples is higher than that of Co86Cr12Ta2 samples, whereas the perpendicular c-axis orientation of Co86Cr12Ta2 samples is better. Ta content was suggested to be in between 2 and 5 at% to give optimum magnetic and structural properties

Intersubtype Reassortments of H5N1 Highly Pathogenic Avian Influenza Viruses Isolated from Quail.

H5N1 highly pathogenic avian influenza (HPAI) viruses are considered a threat to national animal industries, causing production losses and high mortality in domestic poultry. In recent years, quail has become a popular terrestrial poultry species raised for production of meat and eggs in Asia. In this study, to better understand the roles of quail in H5N1 viral evolution, two H5N1-positive samples, designated A/quail/Vietnam/CVVI-49/2010 (CVVI-49/2010) and A/quail/Vietnam/CVVI-50/2014 (CVVI-50/2014), were isolated from quail during H5N1 outbreaks in Vietnam, and their whole genome were analyzed. The phylogenetic analysis reveals new evolutionary variation in the worldwide H5N1 viruses. The quail HA genes were clustered into clades 1.1.1 (CVVI-49/2010) and clade 2.3.2.1c (CVVI-50/2014), which may have evolved from viruses circulating from chickens and/or ducks in Cambodia, mainland of China, Taiwan, Indonesia, and South Korea in recent years. Interestingly, the M2 gene of the CVVI-49/2010 strain contained amino acid substitutions at position 26L-I and 31S-N that are related to amantadine-resistance. In particular, the CVVI-50/2014 strain revealed evidence of multiple intersubtype reassortment events between virus clades 2.3.2.1c, 2.3.2.1b, and 2.3.2.1a. Data from this study supports the possible role of quail as an important intermediate host in avian influenza virus evolution. Therefore, additional surveillance is needed to monitor these HPAI viruses both serologically and virologically in quail

Crystallization and magnetic characterizations of DyIG and HoIG nanopowders fabricated using citrate sol-gel

Dy and Ho iron garnets in form of nanoparticles were synthesized by citrate sol-gel method. Phase formation, lattice constant and average crystallite sizes of the samples were determined via XRD measurements. Morphology and particle size distribution were studied by TEM and chemical composition was checked by EDX. Magnetic measurements in temperature range 5–600 K and in the maximum applied field of 50 kOe were carried out by using SQUID and VSM. Their magnetic parameters, including Curie temperature, magnetization compensation temperature, spontaneous magnetization, high-field susceptibility, magnetic coercivity were discussed in the framework of three interacting magnetic sublattices, magnetocrystalline anisotropy, core-shell model and compared to those of the bulk materials. Based on these analyses further evaluation on the crystallinity and homogeneity of the samples has been made

Proceedings of the International Workshop on Materials Science '95 (IWOMS'95)

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Phylogenetic trees from neighbor-joining analyses of the (a) PA genes, (b) NP genes, (c) M genes, and (d) NS genes of the HPAI H5N1 study strains and reference strains available in the GenBank database.

<p>The tree topology was constructed using the MEGA 6.06 program and bootstrap values were obtained from 1,000 resampled datasets. HPAI H5N1 virus clade names were determined based on specific criteria and reference strains, as described by the World Health Organization, World Organization for Animal Health, and Food and Agricultural Organization. The study strains are marked in bold and black squares.</p

Map of Vietnam showing the study areas.

<p>The HPAI H5N1 outbreaks in quail were located in the highlighted provinces (red, green). Text on the right indicates specific HPAI H5N1 outbreaks and the HPAI H5N1 virus types circulating in northern, central, and southern regions of Vietnam between 2003 and 2014.</p