Peculiarities of the stochastic motion in antiferromagnetic nanoparticles

Antiferromagnetic (AFM) materials are widely used in spintronic devices as passive elements (for stabilization of ferromangetic layers) and as active elements (for information coding). In both cases switching between the different AFM states depends in a great extent from the environmental noise. In the present paper we derive the stochastic Langevin equations for an AFM vector and corresponding Fokker-Planck equation for distribution function in the phase space of generalised coordinate and momentum. Thermal noise is modeled by a random delta-correlated magnetic field that interacts with the dynamic magnetisation of AFM particle. We analyse in details a particular case of the collinear compensated AFM in the presence of spin-polarised current. The energy distribution function for normal modes in the vicinity of two equilibrium states (static and stationary) in sub- and super-critical regimes is found. It is shown that the noise-induced dynamics of AFM vector has pecuilarities compared to that of magnetisation vector in ferromagnets.Comment: Submitted to EPJ ST, presented at the 4-th Conference on Statistical Physics, Lviv, Ukraine, 201

Flights between space debris objects in the vicinity of the geostationary orbit

Abstract: The paper regards the problem of finding the optimal sequence of transfers between large-size space debris objects aimed at their de-orbiting from the vicinity of geostationary orbit (GEO). A flight from one object to another is carried out by a special space vehicle (SV)-collector. It is supposed that an SV approaches a debris object, captures it using a robotic arm and installs a detachable unit on its surface. Using its own propulsion system this unit ensures the object's de-orbiting to the disposal orbit which is situated above GEO region