Dynamics of magnetisation in nano structured materials Event

There are several magnetic systems that serve as theoretical and experimental models for a variety of unusual and interesting dynamics that can occur far from equilibrium. In these models, magnetisation is thought of as a three dimensional vector field that describes the direction of the local magnetic moments, such as those associated with the atoms of a magnetic material. A variety of complex phenomena emerge in magnetic nanostructures where competition and frustration can be introduced geometrically.

An example of engineered frustration is artificial spin ice [1]. We show, using calculations and simulation, that the dynamic evolution of magnetic configurations in square artificial spin ices can be described in terms of quasiparticle 'vertex' excitations, and that vertices interact in a way that can be predicted and understood using nonlinear population equations [2]. We discuss how imperfections and disorder can have significant and interesting consequences on allowed sequences of vertex processes. We show also how controlled access to configurations may be achieved using concepts from network theory [3].

Some mention will also be made of a different sort of dynamics that is itself dependent upon magnetic configurations. In the context of magnetic spin systems, fundamental excitations are called spin waves and are analogous to acoustic waves in elastic media. Spin waves can interact strongly with electromagnetic waves, and the field of study for the resulting excitations is called 'magnonics'. I will discuss some interesting and surprising examples of magnonics with exotic spin configurations that can appear in materials with chiral interactions.

[1] L. Heyderman, R. L. Stamps, J. Phys. Condens. Matter 25, 363201 (2013).
[2] Z. Budrikis, P. Politi, R. L. Stamps, "Vertex dynamics in finite square spin ices", Phys. Rev. Lett. 105, 017201 (2010).
[3] Z. Budrikis, P. Politi, R. L. Stamps, New J. Phys. 14, 045008 (2012)

The talk will run from 4-5pm in B53/4025, Highfield Campus.

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