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A report on very high magnetoimpedance measured at frequencies up to 1.8 GHz in nanostructured [Fe.sub.73.5][Cu.sub.1][Nb.sub.3][Si.sub.13.5][B.sub.9]/Cu film is presented. The results indicate that by playing with the sandwiched and multilayer parameter the response of a magnetoimpedance based sensor could be tuned according to the design needs.

A new study investigates the magnetization dynamics of soft magnetic materials.

The magneto-impedance (MI) effect was investigated in permalloy/Ag multilayers with different Ag thickness and number of bilayer. The magnitude of the MI is substantially increased and the shape of the MI versus H curves transforms from a single-peak centered at H = 0 to a double-peak structure when the Ag thickness is increased from 7 to 25 angstroms. This is due to the different anisotropy axes induced by strain in the multilayers.

Research was conducted to examine the magnetoimpedance (MI) effect on (110)(001)FeSi3% and to study the correlation between the magnetic domain structure evolution and the MI along the hysteresis curve for each sample. Based on data obtained at different frequency ranges, the frequency dependence of the effective transverse differential permeability is derived. Results indicate that the MI measurements are a good complementary tool to study the magnetization processes in highly textured materials.

The stress relief in Finemet ribbons Fe73.5Cu1Nb3Si16.5B6 as a function of the annealing temperature is discussed. The comparison of the as-cast to the sample annealed at 580 degree C verifies the reduction in the internal stress from 15 to 0.2 MPa.

The Barkhausen noise measurements performed on amorphous ribbons Metglas 2605TCA (Fe based), Metglas 2705M (Co based) and Finemet materials with composition Fe73.5Cu1Nb3Si18.5B4 are discussed. The power spectra were found to be sensitive for low stress levels (Fe-based Metglas) and for annealing temperature above 300 degree C.

The magnetoresistance versus bias voltage in NiFe/TaO(sub x)/Al2O3/Co magnetic tunnel junctions is measured. A faster decline of magnetoresistance is observed in samples with 0.5 nm of Ta with the increase in bias voltage.

The power spectra of the Barkhausen noise of Ni1-xMnx was studied to determine the effects of the degree of disorder and of the temperature on domain wall dynamics. The results showed that increased manganese concentration altered the magnetic order from a classical ferromagnetism to a probable mixed state characterized by longitudinal ferromagnetic ordering and spin glass-like transverse frezing.

The field-dependent transverse permeability characterization of amorphous thin films with nominal composition [Fe.sub.73.5][Cu.sub.1][Nb.sub.3][Si.sub.13.5][B.sub.9] is performed for a wide range of frequencies. The dynamic and static magnetic properties of these films are investigated and the obtained results are discussed in terms of the stress contribution to the magnetic anisotropy of the samples.

Magnetoimpedance-based ferromagnetic resonance (FMR) studies of annealed Co68.15Fe4.35Si12.5B15 glass-covered amorphous microwires under stress are reported. Results concluded that a longitudinal anisotropy dominates the microwire behavior under zero stress.

Magnetoimpedence and magnetization measurements are performed in Joule-heated glass-covered amorphous microwires, and impedance spectra are measured at different magnetic fields. The outer shell domains evolve from a circumferential, to a helical structure in the case of the annealed samples, and the inner core evolves from a domain structure typical of a radial anisotropy to a longitudinal one, when the inner core and the outer shell domain structure are observed.

The giant magnetoimpedance of glass-covered amorphous microwires with nominal composition Co70.4Fe4.6Si15B10 is investigated. It is found that the annealing by Joule heating produced a fast crystallization of the sample, decreasing the magnetoimpedance ratio and rounding the peaks observed in Z versus H curves.

Abstract: The degree of micromagnetic disorder in magnetic amorphous materials is investigated by applying the packing method to the time series obtained, both from Barkhausen noise experiments and simulations of domain wall motion. The observed dependences of the estimated entropy on the applied stress, in the case of experimentally obtained time series, and the width of the Gaussian noise used in simulations, are explained in terms of two regimes of the effect of an external stress applied. [Copyright &y& Elsevier]