Doping Of Co Ions Research Articles

Magnetic and electric properties of Co-doped Bi5Ti3FeO15 multiferroic ceramics

Multiferroic ceramics of Bi5Fe1-xCo x Ti3O15(x=0.0—0.6) are synthesized by the conventional solid state reaction, and their microstructure,magnetic and ferroelectric properties are investigated. X-ray diffraction patterns show that a four-layer Aurivillius phase is formed in each sample with a suggested structural transformation at heavy doping of Co ions. The Raman results demonstrate that Co ions enter into the lattice,occupy the B-sites in the BFCT-x and have an effect on the order occupancy of cations at B sites. It is found that the Co ion modification induces remarkable ferromagnetism (FM) at room temperature with a greatest remanent magnetization (2M r) of 2.3 memu/g at x=0.5,which is three orders of magnitude larger than that of Bi5Ti3FeO15(BFTO). All samples with Co doping have ferroelectricity (EM). The remanent polarization (2P r) reaches a value of 11 μC/cm2 at x=0.1,which is about 38.2% higher than that of BFTO,and then decreases when 0.2≤x≤0.4 and increases again at x=0.5 and 0.6. Of all materials,the sample of x=0.5 is best in both good FE and FM.

Structural and Magnetic Properties of Co Doped CeO$_{2}$ Nano-Particles

Nanoparticles of Ce1-xCoxO2 diluted magnetic semiconductors have been prepared by co-precipitation method. Effect of Co substitution has been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM) and DC magnetization measurements. XRD pattern demonstrate that all samples exhibit single phase polycrystalline behavior. The full width at half maximum (FWHM) calculated from XRD pattern has been found to decrease with increase in the Co contents, indicating that particle size decreases with increase in the Co concentration. TEM micrograph reflects the nano-crystalline behavior of all the samples and shows that doping of Co ions hinders growth of the particles. DC magnetization measurements performed at different temperature reveals that Co doped CeO2 exhibits room temperature ferromagnetism.

Effect of Co doping on the magnetotransport properties of La0.45Sr0.55MnO3 perovskite

We investigated the magnetotransport properties of polycrystalline La0.45Sr0.55Mn1−xCoxO3 (0≤x≤0.15). Ferromagnetism is enhanced with the doping of Co ions in La0.45Sr0.55MnO3, but the antiferromagnetism is nearly destroyed in the low-temperature region. The Mn3+–Mn4+ double-exchange (DE) and Co2+–Mn4+ ferromagnetic (FM) superexchange interactions are mainly responsible for the magnetic properties of the doped system. With increased Co doping, the insulating properties and the magnetoresistance (MR) effect are simultaneously enhanced. This indicates that the Co doping strengthens both the Mn3+–Mn4+ DE and Co2+–Mn4+ FM superexchange interactions. The Co doping increases the disorder in the system, causing the MR effect to increase with decreasing temperature.

Studies on structural and magnetic properties of Co-doped pyramidal ZnO nanorods synthesized by solution growth technique

Large-area arrays of highly oriented Co-doped ZnO nanorods with pyramidal hexagonal structure are grown on silica substrates by wet chemical decomposition of zinc–amino complex in an aqueous medium. In case of undoped ZnO with an equi-molar ratio of Zn 2+/hexamethylenetetramine (HMT), highly crystalline nanorods were obtained, whereas for Co-doped ZnO, good quality nanorods were formed at a higher Zn 2+/HMT molar ratio of 4:1. Scanning electron microscope (SEM) studies show the growth of hexagonal-shaped nanorods in a direction nearly perpendicular to the substrate surface with a tip size of ∼50 nm and aspect ratio around 10. The XRD studies show the formation of hexagonal phase pure ZnO with c-axis preferred orientation. The doping of Co ions in ZnO nanorods was confirmed by observation of absorption bands at 658, 617 and 566 nm in the UV–vis spectra of the samples. The optical studies also suggest Co ions to be present both in +2 and +3 oxidation states. From the photoluminescence studies, a defect-related emission is observed in an undoped sample of ZnO at 567 nm. This emission is significantly quenched in Co-doped ZnO samples. Further, the Co-doped nanorods have been found to show ferromagnetic behavior at room temperature from vibrating sample magnetometer (VSM) studies.