New results for the magnitude of flicker noise, considered as resistance fluctuations, in random resistor networks are reported. Near the percolation threshold p c , the magnitude of the relative noise is shown to diverge as (p-p c )~K. The new exponent K is calculated by various methods: Monte Carlo simulations, effective-medium theory, and position-space renormalization group. Exponents pertaining to higher-order cumulants of the resistance fluctuations are also calculated. The possible implications of our results for ongoing experiments on metal-insulator mixtures and cermets are also discussed.

Recent advances in high-density magnetic storage and spin electronics are based on the combined use of magnetic materials with conventional microelectronic materials (metals, insulators and semiconductors). The unit of information (bit) is stored as a magnetization state in some ferromagnetic material (FM) and controlled with an external field altering the magnetization state. As device size is shrinking steadily toward the nanometer and the need to increase the processing bandwidth prevails, racing toward higher frequencies is getting even more challenging. In magnetic systems, denser storage leads to finer magnetic grains and smaller size leads to single magnetic domain physics. The Stoner-Wohlfarth model is the simplest model that describes adequately the physics of fine magnetic grains containing single domains and where magnetization state changes by rotation or switching (abrupt reversal). The SW model is reviewed and discussed with its consequences and potential applications in the physics of magnetism and spin electronics.

A general formulation for the spectral noise S& of random linear resistor networks of arbitrary topology is given. General calculational methods based on Tellegen's theorem are illustrated for oneand two-probe configurations. For self-similar networks, we show the existence of a new exponent b, member of a whole new hierarchy of exponents characterizing the size dependence of the normalized noise spectrum W~--S~/8 . b is shown to lie between the fractal dimension d and the resistance exponent -Pt. . b has been calculated for a large class of fractal structures: Sierpinski gaskets, X lattices, von Koch structures, etc. For percolating systems, W& is investigated for p &p, as well as for p &p, . In particular, an anomalous increase of the noise at p~p, is obtained. A finite-size-scaling function is proposed, and the corresponding exponent b is calculated in mean-field theory.

Measurements and design equations for a two section impedance transforming hybrid suitable for MMIC applications and a new method of synthesis for multisection branch-line hybrids are reported. The synthesis method allows the response to be specified either of Butterworth or Chebyshev type. Both symmetric (with equal input and output impedances) and non-symmetric (impedance transforming) designs are feasible. Starting from a given number of sections, type of response, and impedance transformation ratio and for a specified midband coupling, power division ratio, isolation or directivity ripple bandwidth, the set of constants needed for the evaluation of the reflection coefficient response is first calculated. The latter is used to define a driving point impedance of the circuit, synthesize it and obtain the branch line immittances with the use of the concept of double length unit elements (DLUE). The experimental results obtained with microstrip hybrids constructed to test the validity of the brute force optimization and the synthesized designs show very close agreement with the computed responses.

The physics of magnetic state change in single domain magnetic grains (called Stoner particles) is interesting from the fundamental as well as the applied points of view. A change in magnetization can be finely tuned with a specific time variation of an externally applied magnetic field. It may also occur naturally (without application of a field) at very low temperature with quantum tunneling and at higher temperature with thermal excitation. The optimal (usually shortest) time altering the magnetisation along with the smallest applied magnetic field are sought in technological applications such as high-density reading or writing of information, spintronics, quantum information and quantum communication systems. This work reviews the magnetization change with a time dependent field and temperature and discusses the time it takes to alter the magnetization as a function of the control parameter chosen, temperature and material parameters.

The status of Giant Magneto-Impedance effect is reviewed in wires, ribbons and multilayered soft ferromagnetic thin films. After establishing the theoretical framework for the description of the effect, and the constraints any material should have in order to show the effect, experimental work in wires, ribbons and multilayered thin films is described. Existing and potential applications of the effect in electronics and sensing are highlighted.

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