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The effects of ion irradiation on a giant magnetoimpedance (GMI) have been investigated for a Co-based amorphous ribbon with various kinds of ions such as Xe, Ar, and N. The GMI ratio and M-H loop parameters were used to characterize the samples before and after the ion irradiation. The GMI ratio increased considerably in the ion irradiated samples and the GMI response showed a strong dependence on the irradiated ion species and driving frequencies. It was shown that the ion irradiations lead to a substantial modification of the magnetic properties including a large coercivity and shearing of the in-plane magnetization loops, thus suggesting the reduction of an exchange coupling. [ABSTRACT FROM AUTHOR]

GaMnN and Mg-codoped GaMnN films were grown in molecular beam epitaxy using a GaN single precursor. The structural, electrical, and magnetic properties were examined. The Mg-codoped GaMnN layers revealed room-temperature ferromagnetism. Codoping with Mg reduces the Mn incorporation, but increases the conductivity of the GaMnN films. At the same time, the saturation magnetization and coercivity have increased at room temperature. As this improvement was obtained with much reduced Mn concentration of ∼0.3%, the crucial role of the carriers for carrier-induced ferromagnetism in magnetic semiconductors is observed. [ABSTRACT FROM AUTHOR]

The changes in soft magnetic properties on amorphous Fe[sub 73.5]Cu[sub 1]Nb[sub 3]Si[sub 13.5]B[sub 9] alloy after neutron irradiation are studied by complex permeability spectra, magnetoimpedance ions and M–H curve measurements. The total integration fluence of fast neutrons (n[sub f],E[sub n]>1 MeV) is varied from 1.92×10[sup 14]n[sub f] cm[sup -2] to 4.85×10[sup 16]n[sub f] cm[sup -2]. Two different types of relaxation processes in permeability spectra, which were observed in low and high frequency regions, are related to the domain wall motion and the rotational magnetization, respectively. As neutron irradiation fluence increases, the permeability due to domain wall motion decreases but the permeability due to rotational magnetization increases. The anisotropy field estimated from magnetoimpedance profile decreases with neutron irradiation fluence. The measurement of M–H curves shows the improvement of softness after neutron irradiation of 4.85×10[sup 16]n[sub f] cm[sup -2], due to the enhancement of rotational magnetization. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The N and Ar ions have been irradiated on the Co-based amorphous ribbon to investigate the mechanism of the abrupt increase of the giant magneto-impedance (GM!) response. The M-H loop parameters and grazing incident X-ray diffraction were used to characterize the samples before and after ion irradiation. The GM! ratio increased considerably in the ion irradiated samples and GMI response showed strong dependency on the irradiated ion species and driving frequencies. Substantial modifications of the magnetic properties such as increase of coercivity and change of saturation magnetization were observed in the ion irradiated samples. [ABSTRACT FROM AUTHOR]

Effect of low energy ion beam etching on exchange bias in NiFe/FeMn/NiFe trilayer is investigated in multilayers prepared by rf magnetron sputtering. Stepwise etching and magnetization measurement of FeMn layer in an NiFe/FeMn bilayer show increase of bias as etching proceeds and FeMn thickness decreases. The bias show a maximum around 7 nm FeMn thickness and then fall sharply below 5 nm, broadly in line with the exchange bias variation at increasing FeMn thickness but in reverse order, particularly at low FeMn thickness. Progressive etching of top NiFe layer in the NiFe/FeMn/NiFe trilayer shows an initial gradual increase in bias followed by a sharp increase below 7 nm thickness of top NiFe layer, with a maximum at 2 nm thickness for both NiFe layers and greater bias for seed NiFe layer. [ABSTRACT FROM AUTHOR]