Magnetoelastic effects in Nd4Fe77.5B18.5 nano-composite magnet

In this research, magnetostriction and thermal expansion of polymer-bonded Nd4Fe77.5B18.5 nano-composites are studied using strain gage method. The effect of sintering on samples is also studied. X-ray diffraction patterns and SEM pictures of the original and annealed samples show that the grain size of a -Fe and Fe3B soft magnetic phases in amorphous matrix increases and mechanical hardness of the samples improves after annealing at 700 ° C for 20 min.. Overall behavior of the thermal expansion is similar for samples in both cases, with about 20% larger coefficient for the annealed one. The magnetostriction measurements show huge magnitudes in order of 10-4 at the presence of relatively weak external magnetic fields. The magnitude of magnetostriction noticeably decreases after annealing which can originate from two different sources. Magnetostriction of the original sample mainly originates from single particle interactions of Nd-sublattice in Nd2Fe14B phase, but the situation is very different for the annealed sample. The complicate variations of the magnetostrictive isotherms of the annealed sample are discussed based on the following three factors,internal stresses, magnetocrystalline anisotropy and mechanisms of coercivity

Growth of Cd0.96Zn0.04Te single crystals by vapor phase gas transport method

  Cd0.96Zn0.04Te crystals were grown using vapor phase gas transport method (VPGT). The results show that dendritic crystals with grain size up to 3.5 mm can be grown with this technique. X-ray diffraction and Laue back-reflection patterns show that dendritic crystals are single-phase, whose single crystal grains are randomly oriented with respect to the gas-transport axis. Electrical measurements, carried out using Van der Pauw method, show that the as-grown crystals have resistivity of about 104 Ω cm and n-type conductivity

Magnetostriction and thermal expansion of HoFe11−xCoxTi intermetallic compounds

International audienc

Interaction of hydrogen with Pd- and co-decorated C24 fullerenes: Density functional theory study

In this work, we have investigated the adsorption of a hydrogen atom and molecules on the Pd and Co-decorated C24 fullerenes by means of density functional theory. The hydrogen interaction mechanism with host cages by regarding the adsorption energy and charge density variations was studied. It is found that both Pd and Co atoms have a significant role to increase the adsorption energy as an exothermal process. This energy change is strongly dependent on the electrostatic potential variations around the Pd and Co atoms doped on the C24 fullerene. Also, the HOMO-LUMO gap (Eg) for C24 fullerene varies from 1.20 to 0.76 and 0.86 eV, after decorations of Co and Pd atoms, respectively. More consideration such as thermodynamics parameter, electronic density of states, and charge density analysis are discussed in the context. © 2017 Elsevier B.V

Influence of hydrogenation on structure and magnetic properties of HoFe11−xCoxTi

International audienc

Crystalline structure, magnetic and magnetoelastic properties of Nd6Fe13-xCoxCu intermetallic compounds

Influence of the partial substitution of Co for Fe on the structural, magnetic and magnetoelastic properties of Nd6Fe13Cu compounds are investigated. Analysis of X-ray diffraction patterns indicates that the multi-phase sample is formed for all samples. Upon Co substitution, the second phase Nd2Fe17, Nd2Fe17-yCoy with 0 < y < 1 and Nd2Fe17-zCoz with 1 < z < 2 is formed in the samples with x = 0, 1, 2, respectively so that the lattice parameters are decreased and the Curie temperature is increased. Due to the ferromagnetic phase Nd2Fe17-yCoy in sample with x = 1, the change of the anisotropy and increase of exchange effects are observed. The effects of long-range magnetic ordering processes on Néel temperature clearly appear in the temperature dependence of the spontaneous magnetostriction. Longitudinal (λl) and transverse (λt) magnetostrictions are measured to study the magnetoelastic behaviour of these compounds using a strain gauge method. In the low field region, magnetostrictive strains are small and then increase with increasing fields. Strong pining center of Nd atoms that creates large magnetocrystalline anisotropy prevents easy movement of domain walls. In the sample with x = 0, the magnetostriction contribution from the rare earth sublattice (Nd) dominates at low temperature and the Fe sublattice contribution becomes increasingly important as temperature rises