Materials Literature
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Polycrystalline BiMn2O5 and Bi0.9Ce0.1Mn2O5 have been prepared by a solid-state reaction. A crystalline structure study shows that all x-ray diffraction patterns can be indexed successfully in an orthorhombic phase. Substitution of Ce for Bi ions induced in the unit cell a slight distortion and enlargement. Magnetic a…
We report the development of room-temperature ferromagnetism (FM), with coercivity Hc=2000Oe and saturation magnetization Ms∼0.01emu∕g, in chemically synthesized powders of Zn0.98Co0.02O processed at 150 °C, and paramagnetism with antiferromagnetic interactions between the Co2+ spins (S=3∕2) in samples processed at hi…
We have successfully fabricated composites consisting of aligned Fe flakes embedded in a polymer matrix. Similarly high values of permeability and permittivity have been achieved, resulting in potentially significant improvements in device miniaturization, impedance matching, and bandwidth. Various effective medium th…
We have investigated the magnetocaloric properties on the Ni2Mn1−xAxGa Heusler alloys with partial substitution of Mn by A=Co (x=0.10, 0.20, and 0.30) and Cu (x=0.15 and 0.20) in the vicinity of the martensitic transition by measuring magnetization curves at magnetic field up to 20kOe and in the temperature range of 2…
Ultrathin epitaxial films of NiFe2O4, when grown under specific conditions, show a large enhancement of their magnetic moment and electrical conductivity. This allowed us to use such layers as electrodes in magnetic tunnel junctions. In this paper, we report on the observation of a large tunnel magnetoresistance at lo…
A large positive magnetoresistance (MR) at room temperature was observed in a GaAs:MnAs granular thin film, in which MnAs nanoclusters were embedded in a GaAs matrix. Current-voltage characteristics and a MR effect of the GaAs:MnAs thin film were measured by a two-point-probe method. The MR ratio of the GaAs:MnAs gran…
The magnetic shape-memory effect is a consequence of the coupling between magnetism and structure in ferromagnetic alloys undergoing a martensitic transformation. In these materials large reversible strains can be magnetically induced by the rearrangement of the martensitic twin-variant structure. Several Heusler and…
Mn-doped ZnO diluted magnetic semiconductor (DMS) nanostructures were prepared by direct reaction of zinc metal and manganese chloride powder under oxygen environment using chemical vapor deposition method. Several kinds of nanostructures including nanorod, bowl, and cage were obtained at different deposition temperat…
We have grown heterostructures associating half-metallic La2∕3Sr1∕3MnO3 (LSMO) bottom electrodes and ferromagnetic La0.1Bi0.9MnO3 (LBMO) tunnel barriers. The layers in the heterostructures have good structural properties and top LBMO films (4 nm thick) have a very low roughness when deposited onto LSMO∕SrTiO3(1.6nm) t…
We have investigated the crystal structure and magnetic moment of the Co2FeAl and Co2FeSi films deposited onto thermally oxidized Si and MgO(100) single-crystal substrates, and the structural effect on the tunnel magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs) using a Co2FeZ (Z=Al or Si). The structure…
The temperature dependence of the magnetic anisotropy of ferromagnetic materials is analyzed. Simple ferromagnets, such as Fe and Co, obey the m=n(n+1)∕2 power laws predicted by the Callen and Callen [Phys. Rev. 129, 578 (1963)] theory, but in alloys, the applicability of the theory is an exception rather than the rul…
Nd 2 Fe 14 B ∕ α - Fe isotropic bulk nanocomposite magnets were prepared by spark plasma sintering (SPS) technique using melt-spun powders with a nominated composition of NdxFe94−xB6, with x=6, 8, and 10. It was found that higher sintering temperature improved the densification of the magnets, while it deteriorated th…
The surface magnetic and structural properties of magnetite thin films have been probed by nonlinear second-harmonic generation optical method in high- (centrosymmetric, Oh) and low- (noncentrosymmetric, C1) temperature phases. A model taking into account the cubic magnetocrystalline anisotropy and magnetic symmetry r…
Composite grains, consisting of a subgrain with high anisotropy field coupled with a subgrain with zero anisotropy, are analyzed using a two-spin model. An analytical expression is given for the exchange coupling between the subgrains that minimizes the field required to reverse the magnetically hard layer. The result…
The structural and magnetic properties of arc-melted and homogenized (1300°C, 1h) alloys of Gd5Ge1.9Si2X0.1(X=Cu, Co, Ga, Mn, Al, Bi, or Sn) were investigated by powder x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and magnetometry. The addition of Cu, Ga, Mn, and Al completely elimi…
Magnetic properties of sol-gel-prepared bulk samples of Co0.05Zn0.95O and Mn0.05Zn0.95O are reported before and after annealing in 5%H2∕95%Ar at 573 K for 6 h. The as-prepared samples are paramagnetic with the magnetic susceptibility χ following the Curie-Weiss law: χ=χ0+C∕(T−θ). The magnitudes of C are consistent wit…
Ca2+ controls biological processes by interacting with proteins with different affinities, which are largely influenced by the electrostatic interaction from the local negatively charged ligand residues in the coordination sphere. We have developed a general strategy for rationally designing stable Ca2+- and Ln3+-bind…
Ferrite material properties may vary depending on the grade and manufacturer: there are differences between batches and also the production process may change in time. On the other hand, in power applications, the usual voltage wave forms are closer to square wave than to sine wave, and moreover they contain a dc bias…
We report measurements of the orientations and azimuthal anchoring energies of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) on polycrystalline gold films that are deposited from a vapor at an oblique angle of incidence and subsequently decorated with organized monolayers of oligomers of ethylene glycol.…
Magneto-optical approach for the measurements of complex dielectric permittivity and magnetic permeability of solid and powdered strontium ferrite materials has been performed in the Q-, V-, and W-band frequency ranges. Free-space quasioptical millimeter-wave spectrometer equipped with a backward-wave oscillator as a…