Modelling of magnetic textures in thermal gradients

Laburpena

The total amount of worldwide created data is steadily increasing. All this enormous information is stored in data centres that generate a large amount of heat. Typically, this heat has been considered waste, and the energy needed to cool the data servers is causing the scientific community to search for new paradigms in storage technology. Another challenge facing today's electronics is the miniaturisation of transistors and chips for developing smaller processors, which increases heat dissipation due to the Joule effect. Spincaloritronics constitutes a new concept for heat recovery, which may provide a way for thermal-to-electrical energy conversion. It focuses on the interaction of magnetism and temperature, motivated by finding strategies to improve existing thermoelectric devices. In this context, thermal gradients can be used to convert heat, charge and spin currents. They can also cause the heat-driven dynamics of magnetisation textures. In this regard, controlling nontrivial magnetisation configurations such as domain walls (DWs) and skyrmions is the focus of many research activities due to their potential for new logic and memory devices. The transports of heat, magnetisation (spin) and/or charge are non-equilibrium processes. Various non-equilibrium phenomena occur in ferromagnetic materials, whether metallic or insulating, in which temperature changes produce spin currents (mediated by electrons or magnons). This thesis explores the behaviour of different magnetic structures, such as domain walls and skyrmions, under a thermal gradient in perpendicularly magnetised Co-based thin films. In order to address this topic, we use the micromagnetic approach based on the Landau-Lifshitz-Bloch (LLB) equation, which allows us to model the dynamics of magnetic systems at high temperatures.