Quantum Stochastic Model for Spin Dynamics in Magnetic Systems

We develop a numerical model that reproduces the thermal equilibrium and the spin transfer mechanisms in magnetic materials. We analyze the coherent two-particle spin exchange interaction and the electron-electron collisions. Our study is based on a quantum atomistic approach and the particle dynamics is performed by using a Monte Carlo technique. The coherent quantum evolution of the atoms is interrupted by instantaneous collisions with itinerant electrons. The collision processes are associated to the quantum collapse of the local atomic wave function. We show that particle-particle interactions beyond the molecular field approximation can be included in this framework. Our model is able to reproduce the thermal equilibrium and strongly out-of-equilibrium phenomena such as the ultrafast dynamics of the magnetization in nanomaterials.