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A new study investigates the magnetic properties, microstructure evolution and magnetic domain structures of Co-C films prepared using pulsed-filtered vacuum arc deposition.

A study was conducted on the temperature dependence of annealed Co15Cu85 alloys' magnetic and transport properties from 2 to 300 K. Results show that the resistivity and magnetic property are significantly altered by temperature. A two-current resistance model for computing electron spin-mixing parameter was developed to represent the temperature dependence of magnetoresistance in granular Co15Cu85 alloys.

Pumping by narrow band pulsed Cr:LiSAF and cw Ti:sapphire lasers helps attain high slope efficiency and low threshold laser performance for long pulsed and cw operation at 1.065 micrometer in Nd(super 3+):Sr5(VO4)3F. Spectroscopic studies reveal two inequivalent Nd3+ sites in the crystal. Pumping and lasing efficiencies are diminished by the absorption of Nd3+ ions in secondary sites. Strong concentration quenching of the Nd(3+4)F(3 2) state lowers the quantum efficiency of laser transition from this state.

The spectroscopy properties of Nd3+ doped GdLiF4 (GLF), a laser crystal, are identical with those of Nd:LiYF4 (YLF), another laser crystal. The laser performance of Nd:GLF is also identical with that of Nd:YLF. For a low and high concentration of Nd in GLF, a maximum laser-pump-laser slope efficiency of 68% and 67% was determined respectively. The dipole-dipole interaction between the isolated Nd3+ ions and Nd3+ ion pairs causes the concentration quenching of the fluorescence decay time. The experimental results indicate that the crystals GLF and YLF are isostructural.

High resolution transmission electron microscopy was used to observe epitaxial NiO hillocks on the (111) and (001) facets of truncated octahedral nanoparticles of Ni.

A new study investigates the structure evolution and magnetic properties of amorphous Co-C nanocomposite films fabricated by pulsed vacuum arc deposition.

Magnetization and ac-susceptibility investigation of Fe8 clusters were conducted to gain a deeper understanding of the physics underlying the resonant tunneling of magnetization. The clusters, made of eight iron ions, had a ground state S=10. Peaks in the curves of the samples were observed at fields H(sub n)=nH(sub o). These peaks were well described by the thermally assisted resonant quantum tunneling of magnetization.

A study was conducted to analyze magnetic hysteresis and giant magnetoimpedance in amorphous glass-covered Co-Si-B and Co-Mn-Si-B wires. The influence of the moment rotation and domain wall motion were examined. The dependencies of the modulus of impedance at several frequencies were then analyzed. Experimental results indicated the importance of the rotational component that increases with the field in small fields.

Macroscopic resonant quantum tunneling of magnetization has been seen in antiferromagnetic ferritin particles. The magnetic viscosity dependence on the applied magnetic field was investigated in temperatures between 1.8-10K. Resonant spin tunneling between matching spin levels is thought to contribute to the zero maximum in field dependence of viscosity and maximum n the field dependent blocking temperature.

Analysis of a Cu/Fe granular film obtained from a multilayer film constituted by particles of Fe embedded in Cu, reveals its properties. The properties include magnetic viscosity, ferromagnetic resonance and magnetization. The properties depend on the macroscopic quantum tunneling effect.

The mechanical instabilities of hydrogel microlenses triggered by concentrated loadings are examined. The nontrivial instability pathways have disclosed the richness of the mechanical behavior of hydrogel microlenses and have provided potential strategies to control the design and shape of complex hydrogel microlenses.

Near normal infrared reflectivity spectra of ~550 nm thick films made of cosputtered transition metal nanograins and Si[O.sub.2] in a wide range of metal fractions are reported. A remarkable resonance observed at the angle dependent oblique reflectivity of globally insulating [Co.sub/0.38][(Si[O.sub.2]).sub.0.62], [Fe.sub.0.34][(Si[O.sub.2]).sub.0.66], and [Ni.sub.0.28][(Si[O.sub.2])].sub.0.72] due to the excitation by normal to the film electric fields of defect localized electrons in the metallic nanoparticles are also reported.

A novel transition from the negative exchange bias (NEB) to the positive exchange bias (PEB) because of coexistent and competitive ferromagnetic and antiferromagnetic coupling in a molecular-beam-epitaxy-grown CrSe/Fe/GaAs(111)B structure is described. Phenomenological models are used for describing the mechanism of the PEB effect and the varying asymmetry of the magnetic hysteresis of this structure as a function of the measured temperature.

Core/shell-structured Fe nanoparticles, in which the alpha-Fe core is about 5 nm in diameter and the gamma-Fe2O3 shell is about 3 nm thick, are fabricated. The systematic study of the structural and magnetic properties show large exchange bias and vertical shifts of the field-cooled loops at low temperatures which may be ascribed to the frozen spins in the shells.

The surface and structural properties of Fe implanted on Ge are characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and superconduction quantum interference device (SQUID) magnetometry. The magnetic measurements show the superparamagnetism of the Fe and Fe-Ge clusters at high temperatures.

Exchange bias and inverted hysteresis loops were observed in the Cr2O3 coated CrO2 particles with a wide distribution of the blocking temperature. The ferromagnetic coupling between the CrO2 cores and Cr2O3 shell is responsible for exchange bias observed below 292 K. In the temperature range of 261 K–∼340 K, the particles show inverted hysteresis loops, i.e., the negative remanence and coercivity. The most interesting observation is that the particles show an exchange-biased (or shifted) inverted hysteresis loops in between 261 K and 292 K; and that the maximum negative remanence appears at 292 K where exchange bias disappears. An antiferromagnetic type of interaction between the blocked particles and the superparamagnetic particles is believed to be responsible to the inverted hysteresis loops. [ABSTRACT FROM AUTHOR]

CrO2 particles in digital compact cassette tapes undergo time-dependent magnetic relaxation at low-temperatures. The temperature-dependent magnetic viscosity displays three regimes below room temperature. For temperatures less than 5 Kelvin, the magnetic viscosity is constant, resulting in macroscopic quantum tunneling of magnetization.