Seminar: Finding the path: Various transformations that a magnetic system can undergo and their relevance for thermal stability and optimal control

  • Date: –12:00
  • Location: Ångströmlaboratoriet, Lägerhyddsvägen 1 10238, Beurlingrummet
  • Lecturer: Dr. Pavel Bessarab
  • Contact person: Danny Thonig
  • Seminarium

Identification of paths that are optimal in some sense is an important problem in many areas of science. In this talk, special paths for magnetic systems will be discussed. An important example is minimum energy paths (MEPs) -- paths in the configuration space that connect states with distinct orientation of magnetic moments and lie lowermost on the energy surface. MEPs possess highest statistical weight and, therefore, represent mechanisms of thermally activated magnetic transitions. Combined with the rate theories, MEP calculations make it possible to predict, from first principles, the lifetime of magnetic states at a given temperature, which is important for the design of information storage media based on magnetic elements.

While MEPs define thermal stability of magnetic textures, they generally do not represent deterministic evolution of the magnetic system and, therefore, should be distinguished from dynamical paths that minimize energy losses during switching between target magnetic states. Such 'optimal control paths' (OCPs) give information about energy-efficient control of magnetization and naturally provide solutions for efficient, low-power data processing and recording based on magnetic media. It will be shown that following an OCP involves concerted rotation of magnetic moments in such a way that the system's internal dynamical modes are effectively used to aid the magnetic transition. Various applications of MEP and OCP calculations will be presented, including analysis of thermal stability of magnetic nanoislands and skyrmions as well as spin-wave assisted magnetization switching in nanowires.