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The transport and magnetic properties of Mn xSi1 − x films with a high ( x ≈ 0.35) content of Mn produced by laser deposition at growth temperatures of 300–350°C have been studied in a temperature range of 5–300 K in magnetic fields of up to 2.5 T. The films exhibit a hole-type metallic conductivity and a relatively weak change of magnetization in a temperature range of 50–200 K. An anomalous Hall effect with an essentially hysteretic behavior from 50 K up to ≈230 K has been discovered. The properties of the films are explained by the two-phase model, in which ferromagnetic clusters containing interstitial Mn ions with a localized magnetic moment are embedded in the matrix of a weak band MnSi2 − x ( x ≈ 0.3) type ferromagnet with delocalized spin density. [ABSTRACT FROM AUTHOR]

A superexchange mechanism is considered for the interlayer exchange coupling in Fe/Si nanostructures. It is assumed that the most important role in this mechanism is played by iron-silicon interfaces, in whose immediate vicinity the contact-induced ferromagnetic phase of body-centered iron monosilicide forms and spin-polarized interface states arise. The magnetic coupling between iron layers is accomplished by means of the interaction of interface states through the normal-semiconductor spacer layer and involves both intraband and interband processes. The nonmonotonic character of the dependence of the interband exchange coupling on the spacer thickness and composition (the occurrence of a maximu, the change in shape, the possible sign reversal of the bilinear component) is caused by competition between the ferro-and antiferromagnetic super-exchange components and by the complex character of the spacer electronic spectrum (in particular, by the occurrence of several equivalent extrema in the semiconductor bands). This model qualitatively reproduces the main features of the mechanism of interlayer exchange coupling in real Fe/Si nanostructures. [ABSTRACT FROM AUTHOR]

Magnetic and magnetotransport properties of multilayered nanostructures Co0.45Fe0.45Zr0.1/ a-Si obtained by ion-beam sputtering are investigated. The temperature dependence of the resistance obeys a law of the form R xx ∝-log T, which is typical of metal-insulator nanocomposites on the metal side of the percolation transition. The magnetoresistance anisotropy effect, as well as the planar Hall effect, is observed for the first time for this type of nanocomposites in the vicinity of the percolation transition. The correlation of these two effects with the transverse (between Hall probes) magnetoresistive effect, which may reach 6–9%, is revealed. A weak negative magnetoresistance of the order of 0.15%, which is observed for subnanometer amorphous silicon layer thicknesses, is attributed to spin-dependent electron transitions between adjacent ferromagnetic layers in the case when the exchange interaction between these layers is of the antiferromagnetic type. [ABSTRACT FROM AUTHOR]

We present a theoretical description and electrical conductivity measurements for amorphous (Gd, Y)xSi1 – x alloys with 0.1 < x < 0.2. In our model, we take into account the strong topological disorder in the system, causing the appearance of regions with higher electron density (electron “drops”) around nanoscale structural defects enriched with rare-earth ions (“clusters”). We calculate the local density of electron states in the drops and in the matrix and establish the criterion for local instability to ferromagnetism. In the framework of the “local phase transition” approach, we find that short-range ferromagnetic order is more favorable inside the drops than in the matrix and exists in a wide temperature range. We analyze recent measurements of the temperature and magnetic-field dependence of the electrical conductivity in these systems and show that the spin polarization of the electron states in the drops enhances the tendency towards the metal–insulator transition. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Direct experimental evidence has been obtained for the existence of short-range ferromagnetic order in GdxSi1 – x alloys. Along with the standard magnetotransport measurements, a “local” experimental method of the elastic scattering of thermal neutrons on the magnetic moment of Gd is applied. The measurement results provide the conclusion that short-range ferromagnetic order is formed in nanoclusters with an increased content of Gd ions. We consider the amorphous alloy GdxSi1 – x as a new magnetic material with unique properties characteristic of both strongly inhomogeneous alloys and nanocomposite compounds. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Direct experimental evidence has been obtained for the existence of short-range ferromagnetic order in GdxSi1 – x alloys. Along with the standard magnetotransport measurements, a “local” experimental method of the elastic scattering of thermal neutrons on the magnetic moment of Gd is applied. The measurement results provide the conclusion that short-range ferromagnetic order is formed in nanoclusters with an increased content of Gd ions. We consider the amorphous alloy GdxSi1 – x as a new magnetic material with unique properties characteristic of both strongly inhomogeneous alloys and nanocomposite compounds. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The magnetic phase diagram of the Fe/Cr/Fe three-layer structure with almost ideal interlayer boundaries was constructed. The effective interlayer interaction in this structure was described by the “half-angle coupling” model. Various system configurations were analyzed taking into account crystalline anisotropy, and the ground state of the system was determined. The behavior of the structure in an external magnetic field applied along easy and hard magnetic axes was studied. The magnetization curves M(H) characteristic of structures with various interface roughness parameter and interlayer exchange values were described and analyzed. The experimental situation is discussed. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]