1,721,015 research outputs found
Structure Dependence of the Magnetic-susceptibility Behavior At Low Magnetizing Field
No full textThe magnetic susceptibility during hysteresis cycles was measured in both amorphous and crystalline metallic ribbons. The analysis of the dependence on magnetizing field evidences a different behaviour due to the structural differences. The fundamental importance of the amplitude of the magnetizing field used for dynamic evaluation of initial susceptibility is demonstrated and related to the measured effects as well. Moreover, both temperature and frequency effects on the initial susceptibility confirm some peculiar properties related to the amorphous character
Modello della fluttuazione e stati pre-quantici
No full textGli oscillatori di Bernoulli sono entità di tipo classico sottomesse ad un forzamento che proviene dal vuoto quantistico. Eliminato il rumore quantico dall’equazione del moto, questa assume la forma di un teorema generalizzato di Kapitza per il “grado di libertà classico”. Le densità classiche risolventi si sommano con semplici funzioni di distribuzione all’ appropriata densità quantistica. Se nella transizione allo stato quantico l’effetto tunnel è trascurabile, e il campo di velocità che si arresta alla frontiera classica è dominante, la dinamica dell’oscillatore risulta particolarmente semplice (caso pre-quantico). Gli esempi a ciò più aderenti sono costituiti dagli oscillatori per i quali l’interazione col vuoto è meno forte, per cui gli autovalori dell’energia meccanica restano determinati dalla condizione di invarianza adiabatica classica (regola di Bohr-Sommerfeld)
Magnetomechanical Coupling and Structure of Co1-xpx Alloys Obtained By Electrochemical Deposition
No full textWe have produced ribbons of Co1-xPx (x almost-equal-to 0.09) with the coexistence of microcrystalline and amorphous structure. These kind of materials have different magnetic and magnetostrictive behaviour in comparison with that already known of crystalline or amorphous specimens (x almost-equal-to 0.05 and 0.12, respectively). In particular we demonstrate the obtaining of good magnetoelastic response and, at the same time, the results validate the structure sensitivity of resonant magneto-acoustic waves. The complete behaviour of wave amplitude as a function of the applied magnetization field is compared for each sample and explained
Un modello di evoluzione verso l’equilibrio termodinamico reinterpretato
No full textAlla luce di recenti risultati nel campo della fisica semiclassica dei trasferimenti di energia riconsideriamo un modello standard di evoluzione verso l’equilibrio termodinamico, fondato sulle equazioni di velocità e sulla legge dell’azione di massa, nella sua forma più semplice. Un singolo oscillatore meccanico, di tipo classico, è sottomesso all’azione di un ambiente termodinamico. Le collisioni di tipo esotermico risultano a priori dominanti, ma lo stato energetico dell’oscillatore è sostenuto dall’interazione con il vuoto quantistico. Attraverso un modello di fluttuazione, calcoliamo l’emissività dell’oscillatore in funzione della sua energia meccanica e verifichiamo che il modello riproduce l’evoluzione verso l’equilibrio incorporando le fluttuazioni
Improved model for thermal treatment of metallic ribbons by continuous laser source: Application to amorphous metals
No full textThe thermal model describing the c.w.-annealing of ribbon-shaped materials irradiated by a moving laser beam has been revised and imrpoved. New experimental results on the initial permeability of annealed metallic glasses are presented. © 1983 Società Italiana di Fisica
Stress Sensitivity Coefficient In Polycrystalline and Amorphous Ferromagnetic Materials Below Room-temperature
No full textThe piezomagnetic coupling coefficient (the >) is quantitatively investigated below room temperature and a comparison is made among polycrystalline samples and amorphous ones. The technique used is an original one. It experimentally consists in the measurement of the amplitude of magnetoelastic waves, their resonance frequency and differential susceptibility; theoretically, it consists in coupling Newton's law of force with the piezomagnetic state equations. The results clearly show different responses of polycrystalline samples with respect to the amorphous ones; in particular the nonmonotonic behaviour of the > for metallic glasses is interesting for establishing their actual magnetic states at low temperature
Low temperature behavior of stress sensitivity in polycrystalline, amorphous and multilayer samples
No full textState of the art and development trends of novel nanostructured elastomagnetic composites
No full textThe coupling between elastic and magnetic properties of composite materials made of magnetic particles uniformly dispersed into an elastic matrix was revised. The influence of particles content and size was considered. A unified simple model of the direct and inverse elastomagnetic effect was furnished explaining the experimental results in different experimental conditions. Some applications of elastomagnetic materials in both sensors and actuators are reported and their potentiality is discussed. The correlation between strain and electric conduction in this kind of materials is also presented and the first experimental results on this topic are reported
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