Speaker
Andrea Taroni
(Uppsala University)
Description
The properties of ultrathin magnetic structures are
influenced by many length scales that reflect both
generic physics and chemical detail. A striking example is
the experimentally determined shift of the critical
temperature as a function of film thickness. While all
systems experience a pronounced suppression in Tc with
decreasing film thickness, the magnitude of this shift
cannot be reconciled with established theoretical results.
In particular, the ratio between the monolayer and bulk
limits for the nearest neighbour Ising model is roughly
1/2, whereas experimentally, ratios of the order of 0.1
are commonly measured. By means of detailed Monte
Carlo simulations, we resolve this discrepancy by
investigating a model with long-range interactions. The
model also captures other features of real ultrathin
magnets, such as an almost linear temperature
dependence for the surface magnetization. Our results
demonstrate that the behavior of ultrathin magnetic
structures arises from a competition of length scales
dictated by their slab-like geometry, the presence of
surface boundaries, and crucially, the range of the
interactions present.
Primary author
Andrea Taroni
(Uppsala University)
