Materials Literature
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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…
We use the theory of periodic structures, full-wave electromagnetic, and microwave circuit simulations to explain the resonant modes that propagate in metallic grids having rectangular unit cells constructed over a ground plane. We show that these metallic grids can support two types of resonant modes that have rectan…
Temperature variation (5 K–300 K) of the AC magnetic susceptibilities (χ′ and χ″) at frequency f=0.1, 1, 50, 100, 500, 1000, 2000, 5000, and 10, 000 Hz are reported in 5 nm diameter nanorods of NiO, with and without oleic acid (OA) coating. Using the peak in χ′ as the blocking temperature TB, it is observed that TB in…
Cobalt doping (⩽1%) produces ferromagnetism at room temperature in semiconducting SnO2, presumably due to oxygen vacancies and/or changes in carrier concentration. Electron paramagnetic resonance (EPR) is a sensitive technique to investigate the Co ionic states and their local environments and/or interactions. This pa…
Longitudinal, transverse, and perpendicular magnetoresistances were investigated at temperatures 1.2<T<300K in fields of up to 20 T for four ZnO films: one undoped, two with 4% Co (one paramagnetic, the other exhibiting anhysteretic ferromagnetism at room temperature), and one with 25% Co which exhibits…
The multiferroic rare-earth compounds RMnO3 with R=Ho–Yb are shown to be the source of “gigantic” magnetoelectric effects. Application of static magnetic or electric field induces a phase transition with antiferromagnetic reordering of the Mn3+ sublattice and ferromagnetic ordering in the rare-earth sublattices. An im…
Orthorhombic YMnO3 (YMO) epitaxial thin films were deposited on SrTiO3 (STO) single-crystal substrates. We show that the out-of-plane texture of the YMO films can be tailored using STO substrates having (001), (110), or (111) orientations. We report on the magnetic properties of the YMO(010) films grown on STO(001) su…
The magnetic properties of γ-Fe2O3 ferrimagnetic nanoparticles embedded in a multiblock poly(ether-ester) copolymer have been investigated by static magnetization and ferromagnetic resonance (FMR) measurements at two different dispersion states. Significant variation of the magnetic response is identified below T≈120K…
Patterned recording media consisting of a vertically aligned array of L10 phase CoPt nanowires embedded in a thin anodized aluminum oxide (AAO) template on silicon has been prepared. A sputter deposited thin film of aluminum on silicon was anodized and a CoPt magnetic alloy was electrodeposited into the pores of the A…
Magnetization studies carried out in polycrystalline sample of DyNiAl show the presence of two magnetic transitions, one at 15 K and the other at 30 K. The low-temperature transition is attributed to the onset of antiferromagnetic ordering, while the other one corresponds to the ferro-para transition. Thermomagnetic i…