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Fluctuation and Equilibration in Artificial Magnetic Quasicrystals

Project Description

Frustration is the inability of a physical system to simultaneously satisfy competing
constraints. It occurs across physics and beyond, but is a particularly important topic
in magnetism, a field in which (relatively) simple systems can be represented by toy
statistical mechanical models that can then be extended into other fields model
phenomena as diverse as forest fires and financial networks.

The study of frustration in magnetism has recently been given a new lease of life since
artificial frustrated systems can now be built and studied using nanotechnology: in the
case of magnetism, this is done by constructing arrays of magnetic nanoelements
arranged in patterns where their magnetostatic interactions are frustrated. The
advantages of this approach is that it is possible to build experimental realisations of
models that nature does not provide crystal structures for, with every parameter in the
model tunable by adjusting the element size, shape, and spacing. Moreover, the
microstates of these artificial statistical mechanical systems can be inspected in detail
using advanced magnetic microscopy methods, including time-resolved imaging to
study thermal fluctuations in those microstates.

To date, almost all artificial frustrated spin systems have been ‘crystalline’ in that they
are periodic arrays. In particular, square and hexagonal arrays have been studied as
analogs of spin ice crystals. Thermal excitations in spin ices show appear as emergent
quasiparticles with many of the properties of magnetic monopoles, physics that has
been reproduced in their artificial counterparts. In this project we will study
quasicrystalline systems, where the magnetic nanoelements are arranged on a
Penrose tiling. Whilst small parts of this pattern repeat, the whole pattern never does.
We have begun to study these Penrose-based systems in an athermal state, where
the energy scales are all much larger than kT and so the state of the system is frozen
in. In this project we will build systems that are thermally fluctuating by tuning these
energy scales towards kT. In this way we will study collective nature of the freezing
and melting of the artificial spin system and seek to understand the nature of its
emergent excitations.

How good is research at University of Leeds in Physics?

FTE Category A staff submitted: 24.00

Research output data provided by the Research Excellence Framework (REF)

Click here to see the results for all UK universities

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