Materials Literature
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We report on the properties of ultrathin (2, 4, 6, and 8nm) epitaxial films of magnetite, Fe3O4, grown on MgO (100). Atomic force microscopy image and V-I curves suggest that the films at this thickness are still continuous. The resistivity versus temperature results imply that the conductivity mechanism in all these…
The spontaneous generation of voltage (SGV) in single-crystal and polycrystalline Gd5Si2Ge2 during the coupled magnetostructural transformation has been examined. Our experiments show reversible, measurable, and repeatable SGV responses of the materials to the temperature and magnetic field. The parameters of the resp…
Thermal flux loss (FL) is one of the important properties in applications of Nd–Fe–B magnets to electrical and electronic devices. FL is expected to occur inhomogeneously in magnets with a complex shape, because it depends on the strength of the local demagnetizing field. Thus, in terms of their applications, we need…
The effects of microstructural variations with depth on Barkhausen effect (BE) signals in surface-modified ferrous materials have been studied through measurements and simulations based on a hysteretic-stochastic model. The BE signals measured from an unhardened sample show a peak near zero field. In contrast, the BE…
A measurement method for studying the magnetoelectric effect in pulsed magnetic fields was developed. Besides magnetization, the system allows the measurement of magnetostriction (using strain gauges) and the magnetoelectric effect. For measuring the magnetoelectric effect a special sample holder with fixed contacts a…
In terms of the first-order magnetocrystalline anisotropy energy constant K1, we determined magnetic anisotropy in single-crystalline cubic films having their normal lines parallel to (hkl) axes. We found that the films have biaxial magnetic anisotropy, with which we derived permeability μ(ω)=μ′(ω)−jμ″(ω) (ω: angular…
The dependence of magnetic properties on the film thickness has been studied for Nd–Fe–B films with perpendicular magnetic anisotropy. The W underlayer was used for preventing oxidation of Nd. It is found that the perpendicular coercivity decreases with the increase of the film thickness, although the thick film still…
Starting with 7 nm γFe2O3 nanoparticles, synthesis of DNA-γFe2O3 nanocomposite and its structural/magnetic properties vis-a-vis the parent γFe2O3 are reported. Analysis of the x-ray diffraction shows an increase in the particle strain and average particle size (to 9.7 nm) in DNA-γFe2O3 nanocomposite. Transmission elec…
In order to investigate the effect of annealing conditions on the structural and magnetic properties, we have employed detailed Raman spectroscopic investigations on 5% Fe-doped SnO2 samples annealed at different temperatures in the range 200–900°C. Systematic changes observed in the Raman spectra with increasing anne…
In this work we calculate the magnetocaloric effect in the Laves phase compound RAl2 by using a model Hamiltonian of interacting spins where the spin-spin interaction is treated in the Monte Carlo simulation. The isothermal entropy change and the adiabatic temperature change upon magnetic field variations, for the com…
Composite magnets were prepared by hot pressing followed by hot deformation of blends composed of Nd14Fe79.5Ga0.5B6 or (Nd0.75Dy0.25)14Fe79.5Ga0.5B6 ribbon powders as a high-coercivity component and Fe powder as a high-magnetization component. The addition of 15 wt % α-Fe to (Nd0.75Dy0.25)14Fe79.5Ga0.5B6 increases the…
Highly coercive (Hc up to 37kOe at 300K), high remanent permanent magnets have been achieved by rapid solidification of binary Sm–Co alloys and Sm–Co alloys modified with Nb and C. Rapidly solidified SmCox alloys with x ranging from 5 to 11.5 formed predominantly a solid solution TbCu7-type SmCo7 phase, although hcp C…
We report on measurements of anisotropic magnetoresistance (AMR) (∼ρ‖−ρ⊥) along two orthogonal directions ([001] and [1−10]) of a manganite (La0.95Ag0.05MnO3) epitaxial thin film grown on a (011) SrTiO3 substrate. We show that AMR along [001] is negative whereas along the [1−10] direction is positive at low temperatur…
We report an observation of large magnetocaloric effect in clathrate compounds. Systematic dc magnetization in polycrystalline Eu8Ga16Ge30 clathrates was studied in the temperature range of 5–60 K and over an applied field range of 0–3 T. Change in entropy (ΔSmag) was calculated using the Maxwell relation from the fam…
Thick hard-magnetic films have been prepared from NdFeB microparticles dispersed in polymethylmethacrylate solutions. The preparation process included the application of different magnetic fields during the drying of the hard particles dispersion, which resulted on different degrees of out-of-plane macroscopic anisotr…
We investigate the conformation of atactic poly(sodium 4-styrene sulfonate) (PSS) molecules both in water-ethanol solutions and adsorbed to a template provided by a nanostructured monolayer of flat-lying octadecylamines on graphite. The conformations of the PSS molecules in these solutions undergo two conformational t…
Pure HfO2 and Gd-doped HfO2 thin films have been grown on different single crystal substrates (silicon, R-Al2O3, and LaAlO3) by pulsed laser deposition. X-ray diffraction (XRD) patterns show that the pure HfO2 thin films are of single monoclinic phase. Gd-doped HfO2 films have the same XRD pattern except that their di…
Hysteresis phenomenon is one of the important characteristics of soft magnetic materials. A three-dimensional (3D) magnetic property measurement system has been developed. This system can effectively control the locus of the time-varying magnetic flux density vector B and measure the corresponding magnetic field stren…
Nanocomposite intermediate rare-earth∕high-boron content hard magnetic alloys, having compositions Nd9Fe73B12.6C1.4M4 (M=Ti, V, Cr, Zr, or Nb), have been produced as melt spun ribbon. As for the Ti addition, all the other solutes were effective in modifying the crystallization behavior so that the Nd2Fe14B phase forme…
Structure and magnetic properties of Mn5Ge3−xSix pseudobinary compounds with x=0–1.5 were studied by x-ray diffraction and magnetic measurements. The compounds retain the hexagonal D88-type structure with a space group P63∕mcm, and their lattice parameters decrease from a=7.204(2)Å and c=5.028(2)Å to a=7.084(2)Å and c…