Narrow Results

This paper presents a survey of the methods of statistical physics which are applied to the problem of thermal agitation in magnetic materials. The main focus of the work is the stochastic dynamics described by the Landau-Lifshitz-Gilbert equation for which most analytic results are known, and which has been most commonly used in numerical simulations. We also present the much more recent Landau–Lifshitz–Bloch equation and the numerical calculations describing magnetization dynamics close to the Curie point. The paper is concluded by a description of the newly introduced jump-noise and of the Barkhausen jumps.

We explore the fluctuation theorem for a diffusion in a tilted washboard potential where both the quantum tunneling and the thermal activation play a role. The diffusion process is treated as a biased random walk where the transition rates are enhanced due to the quantum tunneling. Within this framework, the dissipation is easy to handle, since we need not to measure the experimentally inaccessible quantity like total Hamiltonian which includes the bath degrees of freedom.

Electrical noise produced when charges flow through a mesoscopic conductor is non-Gaussian, where higher order cumulants carry valuable information about the microscopic transport process. In these notes we briefly discuss the experimental situation and show that theoretical descriptions for the detection of electrical noise with Josephson junctions lead to generalizations of classical and quantum theories, respectively, for decay rates out of metastable states.

Here in this paper, a multiscale framework based on crystal plasticity is proposed coupling with thermal activation mechanism, as well as the continuum damage mechanism. The microscopic hardening phenomenon is revealed by a dislocation density evolution model, which is constructed according to the temperature. The physical-based exponential function of shear strain rate is posed to describe the thermal material behavior replacing the general phenomenological power-law equation. A 3D spatial distribution of stress, strain and damage is presented in the finite element method, parameters of which are previously determined by a RVE calculation and fitting test compared to the experimental data. Finally, some discussions of stress heterogeneity and texture evolution are proposed and conclusions are made.