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The low frequency magnetic properties and the stress-dependent magnetoimpedance (MI) effect on melt spun CoFeTaB alloys are analyzed. The MI effect is detected for the alloy, with a maximum variation of 1.6% at 5 MHz.

The complex inductance response and the giant magnetoimpedence effect of as-cast CoFeBSiMoNi microwires as a function of frequency and circular field amplitude is examined. The reduced dimension of the microwire indicates higher relaxation frequencies of 3 - 5 * 10(super 6) Hz and larger unpinning field of 127 A/m.

Frequency-dependent magnetic properties of melt spun Fe80B10Si10-xGex (x = 0.0-10.0) were studied by means of inductance spectroscopy (using the complex permeability formalism) and ferromagnetic resonance techniques. The magnetization dynamics showed two magnetization mechanisms, reversible bulging of domains and hysteresis. The dominant mechanism changed as Ge progressively replaced Si; the changes reflect the crystallization processes observed for higher Ge contents, x > 5. High relaxation frequencies (above 1 MHz) were observed for alloys with x ≥ 2.5. In the ferromagnetic resonance response, coupling and decoupling between the amorphous and crystalline phases were detected depending on the orientation of the alloy samples. This allowed the calculation of the anisotropy fields of the alloys-the decreasing trend with increasing Ge content was interpreted in terms of a variable easy direction. [ABSTRACT FROM AUTHOR]

In this work we present a numerical investigation on the magnetic domain formation and magnetization reversal mechanism in submillimeter (250 μm length) amorphous microwires with negative magnetostriction by means of micromagnetic calculations. The formation of circular magnetic domains surrounding an axially, multidomain-oriented central nucleus was observed for the micromagnetic model representing the amorphous microwire. The magnetization reversal described by micromagnetic computations is consistent with a combined nucleation-propagation-rotational mechanism for the magnetization reversal after the saturated state. [ABSTRACT FROM AUTHOR]

The formation and motion of a single cross-tie type domain wall (DW) was studied in a Ni80Fe20 Permalloy nanotube of 50 nm thickness and 500 nm length by means of micromagnetic simulations. Circular magnetization curves, calculated with circumferential ac magnetic fields applied on the nanotube, showed that the propagation of the DW along the nanotube length occurred for hrms values as low as 166 A/m at a frequency of 250 MHz. In general, the observed DW motion exhibited an out-of-phase oscillating character, relative to the applied hac field, with a normalized phase shift of 0.20 being independent of hrms. The DW damping was observed at 10 GHz. [ABSTRACT FROM AUTHOR]

A study of the magnetization process of Co-based amorphous ribbons at low frequencies as a function of decreasing thickness attained by chemical etching was discussed. The results suggested a decreasing tendency of magnetization effect with reduced thickness, while the relaxation frequency exhibited an inverse increasing trend domain-wall free-bulging area.

Coercivity enhancement of REFeAl bulk amorphous alloys was observed upon small B, Cu+B and Dy addition. Results can be attributed to both the existence of small crystallites in the substituted alloys, as well as the presence of RE, REFeAl clusters.

In this report, we present the magnetocaloric effect of Gd1-xYx alloys (0.0⩽ × ⩽0.4) prepared by arc-melting from high purity Gd and Y precursors in inert atmosphere. The formation of Gd1-xYx solid solutions was verified by means of X-ray diffraction analysis across the compositional series; also, residual secondary phases Gd and Y were present. Magnetic characterization performed by Vibrating Sample Magnetometry at a maximum applied field of 3.0 T showed a drastic reduction of the magnetization saturation (from 233 emu/g for x=0.0 to 183 emu/g for x=0.4), due to a dilution effect of the Y alloying, together with a marked Curie temperature decrease from 296K to 196K between x=0.0 and x=0.4. The second-order character of the magnetic transition was established by Arrot plots for all the cases. On the other hand, the magnetic entropy variation, determined from numerical integration of Maxwell relation displayed excellent values above 5.30 J/kg K for alloys with x<0.3 due to the steep transition of the thermomagnetic curves. [ABSTRACT FROM AUTHOR]

Complex inductance formalism (L) is used to calculate the complex circular permeability (μ[SUBcirc) in a domain model for the magnetoimpedance (MI) of soft ferromagnetic wires. An excellent agreement between calculated and experimental values of μ[SUBcirc] as a function of frequency is observed. In addition, a very good agreement is also exhibited between experimental and calculated plots of μ[SUBcirc] as a function of an applied dc magnetic field before and above the relaxation frequency (also known as single- and double-peak MI effect). These results confirm the validity of L as an alternative approach to MI phenomena in soft ferromagnetic wires. [ABSTRACT FROM AUTHOR]

Using off-axis electron holography under Lorentz microscopy conditions to experimentally determine the magnetization distribution in individual cobalt (Co) nanowires, and scanning precession-electron diffraction to obtain their crystalline orientation phase map, allowed us to directly visualize with high accuracy the effect of crystallographic texture on the magnetization of nanowires. The influence of grain boundaries and disorientations on the magnetic structure is correlated on the basis of micromagnetic analysis in order to establish the detailed relationship between magnetic and crystalline structure. This approach demonstrates the applicability of the method employed and provides further understanding on the effect of crystalline structure on magnetic properties at the nanometric scale.